diff --git a/mindspore/lite/include/context.h b/mindspore/lite/include/context.h
index b3f8abe75ef..2623a341890 100644
--- a/mindspore/lite/include/context.h
+++ b/mindspore/lite/include/context.h
@@ -17,8 +17,6 @@
 #ifndef MINDSPORE_LITE_INCLUDE_CONTEXT_H_
 #define MINDSPORE_LITE_INCLUDE_CONTEXT_H_
 
-#include <string>
-#include <memory>
 #include "include/ms_tensor.h"
 #include "include/lite_utils.h"
 #include "include/lite_types.h"
@@ -55,10 +53,14 @@ struct DeviceContext {
 
 /// \brief Context defined for holding environment variables during runtime.
 struct Context {
-  std::string vendor_name_;
+  String vendor_name_;
   int thread_num_ = 2; /**< thread number config for thread pool */
   AllocatorPtr allocator = nullptr;
+#ifndef NOT_USE_STL
   DeviceContextVector device_list_ = {{DT_CPU, {false, MID_CPU}}};
+#else
+  DeviceContextVector device_list_;
+#endif  // NOT_USE_STL
 };
 }  // namespace mindspore::lite
 #endif  // MINDSPORE_LITE_INCLUDE_CONTEXT_H_
diff --git a/mindspore/lite/include/errorcode.h b/mindspore/lite/include/errorcode.h
index b7671259206..9ff4e093795 100644
--- a/mindspore/lite/include/errorcode.h
+++ b/mindspore/lite/include/errorcode.h
@@ -17,8 +17,7 @@
 #ifndef MINDSPORE_LITE_INCLUDE_ERRORCODE_H_
 #define MINDSPORE_LITE_INCLUDE_ERRORCODE_H_
 
-#include <string>
-#include <map>
+#include "include/lite_utils.h"
 
 namespace mindspore {
 namespace lite {
@@ -67,7 +66,7 @@ constexpr int RET_INPUT_PARAM_INVALID = -600; /**< Invalid input param by user.
 /// \param[in] error_code define return status of procedure.
 ///
 /// \return String of errorcode info.
-std::string GetErrorInfo(STATUS error_code);
+String GetErrorInfo(STATUS error_code);
 
 }  // namespace lite
 }  // namespace mindspore
diff --git a/mindspore/lite/include/lite_session.h b/mindspore/lite/include/lite_session.h
index e2eed86a7b4..c3ad559339f 100644
--- a/mindspore/lite/include/lite_session.h
+++ b/mindspore/lite/include/lite_session.h
@@ -17,10 +17,9 @@
 #ifndef MINDSPORE_LITE_INCLUDE_LITE_SESSION_H
 #define MINDSPORE_LITE_INCLUDE_LITE_SESSION_H
 
-#include <memory>
-#include <vector>
-#include <string>
+#ifndef NOT_USE_STL
 #include <unordered_map>
+#endif  // NOT_USE_STL
 #include "include/ms_tensor.h"
 #include "include/model.h"
 #include "include/context.h"
@@ -66,14 +65,14 @@ class MS_API LiteSession {
   /// \brief Get input MindSpore Lite MSTensors of model.
   ///
   /// \return The vector of MindSpore Lite MSTensor.
-  virtual std::vector<tensor::MSTensor *> GetInputs() const = 0;
+  virtual Vector<tensor::MSTensor *> GetInputs() const = 0;
 
   /// \brief Get input MindSpore Lite MSTensors of model by tensor name.
   ///
   /// \param[in] node_name Define tensor name.
   ///
   /// \return The vector of MindSpore Lite MSTensor.
-  virtual mindspore::tensor::MSTensor *GetInputsByTensorName(const std::string &tensor_name) const = 0;
+  virtual mindspore::tensor::MSTensor *GetInputsByTensorName(const String &tensor_name) const = 0;
 
   /// \brief Run session with callback.
   ///
@@ -92,24 +91,26 @@ class MS_API LiteSession {
   /// \note Deprecated, replace with GetOutputByTensorName
   ///
   /// \return The vector of MindSpore Lite MSTensor.
-  virtual std::vector<tensor::MSTensor *> GetOutputsByNodeName(const std::string &node_name) const = 0;
+  virtual Vector<tensor::MSTensor *> GetOutputsByNodeName(const String &node_name) const = 0;
 
+#ifndef NOT_USE_STL
   /// \brief Get output MindSpore Lite MSTensors of model mapped by tensor name.
   ///
   /// \return The map of output tensor name and MindSpore Lite MSTensor.
-  virtual std::unordered_map<std::string, mindspore::tensor::MSTensor *> GetOutputs() const = 0;
+  virtual std::unordered_map<String, mindspore::tensor::MSTensor *> GetOutputs() const = 0;
+#endif
 
   /// \brief Get name of output tensors of model compiled by this session.
   ///
   /// \return The vector of string as output tensor names in order.
-  virtual std::vector<std::string> GetOutputTensorNames() const = 0;
+  virtual Vector<String> GetOutputTensorNames() const = 0;
 
   /// \brief Get output MindSpore Lite MSTensors of model by tensor name.
   ///
   /// \param[in] tensor_name Define tensor name.
   ///
   /// \return Pointer of MindSpore Lite MSTensor.
-  virtual mindspore::tensor::MSTensor *GetOutputByTensorName(const std::string &tensor_name) const = 0;
+  virtual mindspore::tensor::MSTensor *GetOutputByTensorName(const String &tensor_name) const = 0;
 
   /// \brief Resize inputs shape.
   ///
@@ -117,7 +118,7 @@ class MS_API LiteSession {
   /// \param[in] dims Define the inputs new shape.
   ///
   /// \return STATUS as an error code of resize inputs, STATUS is defined in errorcode.h.
-  virtual int Resize(const std::vector<tensor::MSTensor *> &inputs, const std::vector<std::vector<int>> &dims) = 0;
+  virtual int Resize(const Vector<tensor::MSTensor *> &inputs, const Vector<Vector<int>> &dims) = 0;
 };
 }  // namespace session
 }  // namespace mindspore
diff --git a/mindspore/lite/include/lite_utils.h b/mindspore/lite/include/lite_utils.h
index 1b22677a9a8..d7ebedbc12e 100644
--- a/mindspore/lite/include/lite_utils.h
+++ b/mindspore/lite/include/lite_utils.h
@@ -16,31 +16,383 @@
 
 #ifndef MINDSPORE_LITE_INCLUDE_LITE_UTILS_H_
 #define MINDSPORE_LITE_INCLUDE_LITE_UTILS_H_
+
+#ifndef NOT_USE_STL
 #include <vector>
 #include <string>
 #include <memory>
-#include "include/ms_tensor.h"
+#include <functional>
+#else
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stddef.h>
+#endif  // NOT_USE_STL
+
+#ifndef MS_API
+#ifdef _WIN32
+#define MS_API __declspec(dllexport)
+#else
+#define MS_API __attribute__((visibility("default")))
+#endif
+#endif
 
 namespace mindspore {
-class Allocator;
-
 namespace schema {
 struct Tensor;
 }  // namespace schema
 
+namespace tensor {
+class MSTensor;
+}  // namespace tensor
+
 namespace lite {
+struct DeviceContext;
+}  // namespace lite
+
+#ifdef NOT_USE_STL
+class String {
+ public:
+  String();
+  String(size_t count, char ch);
+  String(const char *s, size_t count);
+  explicit String(const char *s);
+  String(const String &other);
+  String(const String &other, size_t pos, size_t count = npos);
+
+  ~String();
+
+  String &operator=(const String &str);
+  String &operator=(const char *str);
+
+  char &at(size_t pos);
+  const char &at(size_t pos) const;
+  inline char &operator[](size_t pos);
+  inline const char &operator[](size_t pos) const;
+  char *data() noexcept;
+  const char *data() const noexcept;
+  const char *c_str() const noexcept;
+
+  // capacity
+  bool empty() const noexcept;
+  size_t size() const noexcept;
+  size_t length() const noexcept;
+
+  // operations
+  void clear() noexcept;
+  String &append(size_t count, const char ch);
+  String &append(const String &str);
+  String &append(const char *s);
+  String &operator+(const String &str);
+  String &operator+=(const String &str);
+  String &operator+=(const char *str);
+  String &operator+=(const char ch);
+  int compare(const String &str) const;
+  int compare(const char *str) const;
+
+  String substr(size_t pos = 0, size_t count = npos) const;
+
+  static const size_t npos = -1;
+
+ private:
+  size_t size_;
+  char *buffer_;
+};
+
+String operator+(const String &str1, const char *str2);
+String operator+(const char *str1, const String &str2);
+
+String to_string(int32_t value);
+String to_string(float value);
+
+#define DEFAULT_CAPACITY 4
+#define MS_C_EXCEPTION(...) exit(1)
+#define MIN(x, y) ((x < y) ? (x) : (y))
+template <typename T>
+class Vector {
+ public:
+  Vector() {
+    size_ = 0;
+    capacity_ = DEFAULT_CAPACITY;
+    elem_size_ = sizeof(T);
+    data_ = nullptr;
+  }
+
+  explicit Vector(size_t size) {
+    size_ = size;
+    elem_size_ = sizeof(T);
+    capacity_ = (size == 0 ? DEFAULT_CAPACITY : size);
+    data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+    if (data_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    memset(data_, 0, capacity_ * elem_size_);
+  }
+
+  Vector(size_t size, const T &value) {
+    size_ = size;
+    elem_size_ = sizeof(T);
+    capacity_ = (size == 0 ? DEFAULT_CAPACITY : size);
+    data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+    if (data_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    for (int i = 0; i < size; ++i) {
+      data_[i] = value;
+    }
+  }
+
+  Vector(const Vector<T> &vec) {
+    size_ = vec.size_;
+    elem_size_ = sizeof(T);
+    capacity_ = vec.capacity_;
+    data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+    if (data_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    memcpy(data_, vec.data_, size_ * elem_size_);
+  }
+
+  ~Vector() {
+    if (data_ != nullptr) {
+      free(data_);
+    }
+  }
+
+  void clear() {
+    size_ = 0;
+    if (data_ != nullptr) {
+      free(data_);
+      data_ = nullptr;
+    }
+  }
+
+  void push_back(const T &elem) {
+    if (data_ == nullptr) {
+      data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+      if (data_ == nullptr) {
+        MS_C_EXCEPTION("malloc data failed");
+      }
+    } else if (size_ == capacity_) {
+      resize(size_ + 1);
+      --size_;
+    }
+    data_[size_] = elem;
+    ++size_;
+  }
+
+  void push_back(T &&elem) {
+    if (data_ == nullptr) {
+      data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+      if (data_ == nullptr) {
+        MS_C_EXCEPTION("malloc data failed");
+      }
+    } else if (size_ == capacity_) {
+      resize(size_ + 1);
+      --size_;
+    }
+    data_[size_] = elem;
+    ++size_;
+  }
+
+  void pop_back() {
+    if (size_ > 0) {
+      --size_;
+    } else {
+      MS_C_EXCEPTION("Index is out of range!");
+    }
+  }
+
+  void insert(const T &elem, size_t index) {
+    if (index <= size_) {
+      ++size_;
+      if (size_ > capacity_) {
+        resize(size_);
+      }
+      if (index == size_ - 1) {
+        push_back(elem);
+      } else {
+        memmove(data_ + index + 1, data_ + index, (size_ - index - 1) * elem_size_);
+        data_[index] = elem;
+      }
+    } else {
+      MS_C_EXCEPTION("Input index is out of range!");
+    }
+  }
+
+  T *begin() { return data_; }
+
+  const T *begin() const { return data_; }
+
+  T *end() { return data_ + size_; }
+
+  const T *end() const { return data_ + size_; }
+
+  T &front() {
+    if (size_ > 0) {
+      return data_[0];
+    }
+    MS_C_EXCEPTION("Index is out of range!");
+  }
+
+  const T &front() const {
+    if (size_ > 0) {
+      return data_[0];
+    }
+    MS_C_EXCEPTION("Index is out of range!");
+  }
+
+  T &back() {
+    if (size_ > 0) {
+      return data_[size_ - 1];
+    }
+    MS_C_EXCEPTION("Index is out of range!");
+  }
+
+  const T &back() const {
+    if (size_ > 0) {
+      return data_[size_ - 1];
+    }
+    MS_C_EXCEPTION("Index is out of range!");
+  }
+
+  T &at(size_t index) {
+    if (index < size_) {
+      return data_[index];
+    }
+    MS_C_EXCEPTION("Input index is out of range!");
+  }
+
+  const T &at(size_t index) const {
+    if (index < size_) {
+      return data_[index];
+    }
+    MS_C_EXCEPTION("Input index is out of range!");
+  }
+
+  T &operator[](size_t index) {
+    if (index < size_) {
+      return data_[index];
+    }
+    MS_C_EXCEPTION("Input index is out of range!");
+  }
+
+  const T &operator[](size_t index) const {
+    if (index < size_) {
+      return data_[index];
+    }
+    MS_C_EXCEPTION("Input index is out of range!");
+  }
+
+  T *data() { return data_; }
+
+  const T *data() const { return data_; }
+
+  size_t size() const { return size_; }
+
+  size_t capacity() const { return capacity_; }
+
+  bool empty() const { return size_ == 0; }
+
+  void erase(size_t index) {
+    if (index == size_ - 1) {
+      --size_;
+    } else if (index < size_) {
+      memmove(data_ + index, data_ + index + 1, (size_ - index - 1) * elem_size_);
+      --size_;
+    } else {
+      MS_C_EXCEPTION("Input index is out of range!");
+    }
+  }
+
+  void resize(size_t size) {
+    while (size > capacity_) {
+      capacity_ *= 2;
+    }
+    T *tmp = data_;
+    data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+    if (data_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    memcpy(data_, tmp, MIN(size, size_) * elem_size_);
+    size_ = size;
+    free(tmp);
+  }
+
+  void reserve(size_t capacity) {
+    if (capacity > capacity_) {
+      capacity_ = capacity;
+    }
+  }
+
+  Vector<T> &operator=(const Vector<T> &vec) {
+    if (this == &vec) {
+      return *this;
+    }
+    size_ = vec.size_;
+    elem_size_ = sizeof(T);
+    capacity_ = vec.capacity_;
+    data_ = reinterpret_cast<T *>(malloc(capacity_ * elem_size_));
+    if (data_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    memcpy(data_, vec.data_, size_ * elem_size_);
+    return *this;
+  }
+
+ private:
+  size_t size_;
+  size_t elem_size_;
+  size_t capacity_;
+  T *data_;
+};
+using TensorPtrVector = Vector<mindspore::schema::Tensor *>;
+using Uint32Vector = Vector<uint32_t>;
+using AllocatorPtr = void *;
+using DeviceContextVector = Vector<lite::DeviceContext>;
+using KernelCallBack = void (*)(void *, void *);
+#else
 /// \brief Allocator defined a memory pool for malloc memory and free memory dynamically.
 ///
 /// \note List public class and interface for reference.
-
-/// \brief DeviceContext defined a device context.
-struct DeviceContext;
+class Allocator;
+using AllocatorPtr = std::shared_ptr<Allocator>;
 
 using TensorPtrVector = std::vector<mindspore::schema::Tensor *>;
-using DeviceContextVector = std::vector<DeviceContext>;
 using Uint32Vector = std::vector<uint32_t>;
+template <typename T>
+using Vector = std::vector<T>;
+
+template <typename T>
+inline std::string to_string(T t) {
+  return std::to_string(t);
+}
+
+namespace tensor {
 using String = std::string;
-using AllocatorPtr = std::shared_ptr<Allocator>;
+}  // namespace tensor
+
+namespace session {
+using String = std::string;
+}  // namespace session
+
+/// \brief CallBackParam defined input arguments for callBack function.
+struct CallBackParam {
+  session::String node_name; /**< node name argument */
+  session::String node_type; /**< node type argument */
+};
+
+struct GPUCallBackParam : CallBackParam {
+  double execute_time{-1.f};
+};
+
+/// \brief KernelCallBack defined the function pointer for callBack.
+using KernelCallBack = std::function<bool(Vector<tensor::MSTensor *> inputs, Vector<tensor::MSTensor *> outputs,
+                                          const CallBackParam &opInfo)>;
+
+namespace lite {
+using String = std::string;
+using DeviceContextVector = std::vector<DeviceContext>;
 
 /// \brief Set data of MSTensor from string vector.
 ///
@@ -48,12 +400,13 @@ using AllocatorPtr = std::shared_ptr<Allocator>;
 /// \param[out] MSTensor.
 ///
 /// \return STATUS as an error code of this interface, STATUS is defined in errorcode.h.
-int MS_API StringsToMSTensor(const std::vector<std::string> &inputs, tensor::MSTensor *tensor);
+int MS_API StringsToMSTensor(const Vector<String> &inputs, tensor::MSTensor *tensor);
 
 /// \brief Get string vector from MSTensor.
 /// \param[in] MSTensor.
 /// \return string vector.
-std::vector<std::string> MS_API MSTensorToStrings(const tensor::MSTensor *tensor);
+Vector<String> MS_API MSTensorToStrings(const tensor::MSTensor *tensor);
 }  // namespace lite
+#endif  // NOT_USE_STL
 }  // namespace mindspore
 #endif  // MINDSPORE_LITE_INCLUDE_LITE_UTILS_H_
diff --git a/mindspore/lite/include/model.h b/mindspore/lite/include/model.h
index 6fa57be574e..22d2ffa30b9 100644
--- a/mindspore/lite/include/model.h
+++ b/mindspore/lite/include/model.h
@@ -15,7 +15,7 @@
  */
 #ifndef MINDSPORE_LITE_INCLUDE_MODEL_H_
 #define MINDSPORE_LITE_INCLUDE_MODEL_H_
-#include <vector>
+
 #include "include/lite_utils.h"
 
 namespace mindspore::lite {
@@ -28,7 +28,7 @@ struct MS_API Model {
     Uint32Vector output_indices_;
     int quant_type_;
   };
-  using NodePtrVector = std::vector<Node *>;
+  using NodePtrVector = Vector<Node *>;
   struct SubGraph {
     String name_;
     Uint32Vector input_indices_;
@@ -36,7 +36,7 @@ struct MS_API Model {
     Uint32Vector node_indices_;
     Uint32Vector tensor_indices_;
   };
-  using SubGraphPtrVector = std::vector<SubGraph *>;
+  using SubGraphPtrVector = Vector<SubGraph *>;
   String name_;
   String version_;
   TensorPtrVector all_tensors_;
diff --git a/mindspore/lite/include/ms_tensor.h b/mindspore/lite/include/ms_tensor.h
index 6d038232553..1a6f3112b8a 100644
--- a/mindspore/lite/include/ms_tensor.h
+++ b/mindspore/lite/include/ms_tensor.h
@@ -17,21 +17,9 @@
 #ifndef MINDSPORE_LITE_INCLUDE_MS_TENSOR_H_
 #define MINDSPORE_LITE_INCLUDE_MS_TENSOR_H_
 
-#include <functional>
-#include <memory>
-#include <string>
-#include <utility>
-#include <vector>
+#include "include/lite_utils.h"
 #include "ir/dtype/type_id.h"
 
-#ifndef MS_API
-#ifdef _WIN32
-#define MS_API __declspec(dllexport)
-#else
-#define MS_API __attribute__((visibility("default")))
-#endif
-#endif
-
 namespace mindspore {
 namespace tensor {
 /// \brief MSTensor defined tensor in MindSpore Lite.
@@ -48,7 +36,7 @@ class MS_API MSTensor {
   /// \brief Create a MSTensor.
   ///
   /// \return Pointer to an instance of MindSpore Lite MSTensor.
-  static MSTensor *CreateTensor(const std::string &name, TypeId type, const std::vector<int> &shape, const void *data,
+  static MSTensor *CreateTensor(const String &name, TypeId type, const Vector<int> &shape, const void *data,
                                 size_t data_len);
 
   /// \brief Get data type of the MindSpore Lite MSTensor.
@@ -62,10 +50,10 @@ class MS_API MSTensor {
   /// \brief Get shape of the MindSpore Lite MSTensor.
   ///
   /// \return A vector of int as the shape of the MindSpore Lite MSTensor.
-  virtual std::vector<int> shape() const = 0;
+  virtual Vector<int> shape() const = 0;
 
   /// \brief Set the shape of MSTensor.
-  virtual void set_shape(const std::vector<int> &name) = 0;
+  virtual void set_shape(const Vector<int> &name) = 0;
 
   /// \brief Get number of element in MSTensor.
   ///
@@ -80,10 +68,10 @@ class MS_API MSTensor {
   /// \brief Get the name of MSTensor.
   ///
   /// \return the name of MSTensor.
-  virtual std::string tensor_name() const = 0;
+  virtual String tensor_name() const = 0;
 
   /// \brief Set the name of MSTensor.
-  virtual void set_tensor_name(const std::string name) = 0;
+  virtual void set_tensor_name(const String name) = 0;
 
   /// \brief Get the pointer of data in MSTensor.
   ///
@@ -105,18 +93,5 @@ class MS_API MSTensor {
   virtual void set_data(void *data) = 0;
 };
 }  // namespace tensor
-/// \brief CallBackParam defined input arguments for callBack function.
-struct CallBackParam {
-  std::string node_name; /**< node name argument */
-  std::string node_type; /**< node type argument */
-};
-
-struct GPUCallBackParam : CallBackParam {
-  double execute_time{-1.f};
-};
-
-/// \brief KernelCallBack defined the function pointer for callBack.
-using KernelCallBack = std::function<bool(std::vector<tensor::MSTensor *> inputs,
-                                          std::vector<tensor::MSTensor *> outputs, const CallBackParam &opInfo)>;
 }  // namespace mindspore
 #endif  // MINDSPORE_LITE_INCLUDE_MS_TENSOR_H_
diff --git a/mindspore/lite/include/version.h b/mindspore/lite/include/version.h
index 476fc20625d..8a9ca730e71 100644
--- a/mindspore/lite/include/version.h
+++ b/mindspore/lite/include/version.h
@@ -17,7 +17,7 @@
 #ifndef MINDSPORE_LITE_INCLUDE_VERSION_H_
 #define MINDSPORE_LITE_INCLUDE_VERSION_H_
 
-#include <string>
+#include "include/lite_utils.h"
 
 namespace mindspore {
 namespace lite {
@@ -28,11 +28,11 @@ const int ms_version_revision = 0;
 /// \brief Global method to get a version string.
 ///
 /// \return The version string of MindSpore Lite.
-inline std::string Version() {
-  return "MindSpore Lite " + std::to_string(ms_version_major) + "." + std::to_string(ms_version_minor) + "." +
-         std::to_string(ms_version_revision);
+inline String Version() {
+  return "MindSpore Lite " + to_string(ms_version_major) + "." + to_string(ms_version_minor) + "." +
+         to_string(ms_version_revision);
 }
 }  // namespace lite
 }  // namespace mindspore
 
-#endif  // LITE_VERSION_H
+#endif  // MINDSPORE_LITE_INCLUDE_VERSION_H_
diff --git a/mindspore/lite/micro/cmake/package_wrapper.cmake b/mindspore/lite/micro/cmake/package_wrapper.cmake
index 54bc68e226e..094af3886e3 100644
--- a/mindspore/lite/micro/cmake/package_wrapper.cmake
+++ b/mindspore/lite/micro/cmake/package_wrapper.cmake
@@ -22,6 +22,7 @@ set(WRAPPER_SRC
         ${WRAPPER_DIR}/int8/resize_int8_wrapper.c
         ${WRAPPER_DIR}/int8/slice_int8_wrapper.c
         ${WRAPPER_DIR}/int8/batchnorm_int8_wrapper.c
+        ${LITE_DIR}/src/common/string.cc
         )
 
 list(APPEND FILE_SET ${WRAPPER_SRC} ${RUNTIME_SRC})
diff --git a/mindspore/lite/micro/coder/generator/component/cmake_component.cc b/mindspore/lite/micro/coder/generator/component/cmake_component.cc
index c43e87900d7..f263a7ff96b 100644
--- a/mindspore/lite/micro/coder/generator/component/cmake_component.cc
+++ b/mindspore/lite/micro/coder/generator/component/cmake_component.cc
@@ -34,7 +34,8 @@ void CodeCMakeNetLibrary(std::ofstream &ofs, const std::unique_ptr<CoderContext>
   ofs << "    weight.c.o\n"
       << "    net.c.o\n"
       << "    session.cc.o\n"
-      << "    tensor.cc.o\n";
+      << "    tensor.cc.o\n"
+      << "    string.cc.o\n";
   if (config->debug_mode()) {
     ofs << "    debug_utils.c.o\n";
   }
diff --git a/mindspore/lite/micro/coder/generator/component/common_component.cc b/mindspore/lite/micro/coder/generator/component/common_component.cc
index fa46f32d85d..85bae959bbc 100644
--- a/mindspore/lite/micro/coder/generator/component/common_component.cc
+++ b/mindspore/lite/micro/coder/generator/component/common_component.cc
@@ -26,6 +26,14 @@
 
 namespace mindspore::lite::micro {
 void CodeSessionCompileGraph(std::ofstream &ofs, const std::unique_ptr<CoderContext> &ctx) {
+  auto array_tostring = [&ofs](const std::vector<int> &array, const std::string &name) {
+    size_t num = array.size();
+    ofs << "  Vector<int> " << name << ";\n";
+    ofs << "  " << name << ".resize(" << num << ");\n";
+    for (size_t i = 0; i < num; ++i) {
+      ofs << "  " << name << "[" << i << "] = " << array[i] << ";\n";
+    }
+  };
   std::vector<Tensor *> inputs = ctx->graph_inputs();
   std::vector<Tensor *> outputs = ctx->graph_outputs();
   size_t inputs_size = inputs.size();
@@ -36,20 +44,21 @@ void CodeSessionCompileGraph(std::ofstream &ofs, const std::unique_ptr<CoderCont
   ofs << "  inputs_.resize(" << inputs_size << ");\n";
   for (size_t i = 0; i < inputs_size; ++i) {
     Tensor *input = inputs[i];
-    ofs << "  inputs_[" << i << "] = new (std::nothrow) MTensor(\"" << input->tensor_name() << "\", "
-        << EnumNameDataType(input->data_type()) << ", " << ArrayToString(input->shape()) << ");\n";
+    std::string shape_i = "in_shape_" + std::to_string(i);
+    array_tostring(input->shape(), shape_i);
+    ofs << "  inputs_[" << i << "] = new (std::nothrow) MTensor(String(\"" << input->tensor_name() << "\"), "
+        << EnumNameDataType(input->data_type()) << ", " << shape_i << ");\n";
     ofs << "  MS_ERROR_IF_NULL(inputs_[" << i << "]);\n";
   }
   ofs << "  outputs_.resize(" << outputs_size << ");\n";
   for (size_t i = 0; i < outputs_size; ++i) {
     Tensor *output = outputs[i];
-    ofs << "  outputs_[" << i << "] = new (std::nothrow) MTensor(\"" << output->tensor_name() << "\", "
-        << EnumNameDataType(output->data_type()) << ", " << ArrayToString(output->shape()) << ");\n";
+    std::string shape_i = "out_shape_" + std::to_string(i);
+    array_tostring(output->shape(), shape_i);
+    ofs << "  outputs_[" << i << "] = new (std::nothrow) MTensor(String(\"" << output->tensor_name() << "\"), "
+        << EnumNameDataType(output->data_type()) << ", " << shape_i << ");\n";
     ofs << "  MS_ERROR_IF_NULL(outputs_[" << i << "]);\n";
   }
-  ofs << "  for (const auto &output: outputs_) {\n"
-         "    output_tensor_map_[output->tensor_name()] = output;\n"
-         "  }\n";
   ofs << "  return RET_OK;\n";
   ofs << "}\n\n";
 }
diff --git a/mindspore/lite/micro/coder/generator/component/const_blocks/benchmark.cc b/mindspore/lite/micro/coder/generator/component/const_blocks/benchmark.cc
index 929ab824033..0a13a05956f 100644
--- a/mindspore/lite/micro/coder/generator/component/const_blocks/benchmark.cc
+++ b/mindspore/lite/micro/coder/generator/component/const_blocks/benchmark.cc
@@ -72,10 +72,6 @@ void PrintData(void *data, size_t data_number) {
 }
 
 void TensorToString(tensor::MSTensor *tensor) {
-  uint8_t i = 0;
-  std::cout << "uint8: " << i << std::endl;
-
-  std::cout << "Name: " << tensor->tensor_name();
   std::cout << ", DataType: " << tensor->data_type();
   std::cout << ", Size: " << tensor->Size();
   std::cout << ", Shape:";
@@ -129,7 +125,7 @@ int main(int argc, const char **argv) {
   }
 
   // set model inputs tensor data
-  std::vector<tensor::MSTensor *> inputs = session->GetInputs();
+  Vector<tensor::MSTensor *> inputs = session->GetInputs();
   size_t inputs_num = inputs.size();
   void *inputs_binbuf[inputs_num];
   int inputs_size[inputs_num];
@@ -150,13 +146,6 @@ int main(int argc, const char **argv) {
     return lite::RET_ERROR;
   }
 
-  auto outputs = session->GetOutputs();
-  std::cout << "output size: " << outputs.size() << std::endl;
-  for (const auto &item : outputs) {
-    auto output = item.second;
-    TensorToString(output);
-  }
-
   std::cout << "run benchmark success" << std::endl;
   delete session;
   for (size_t i = 0; i < inputs_num; ++i) {
diff --git a/mindspore/lite/micro/coder/generator/component/const_blocks/cmake_lists.cc b/mindspore/lite/micro/coder/generator/component/const_blocks/cmake_lists.cc
index b306c153cb0..21080094c28 100644
--- a/mindspore/lite/micro/coder/generator/component/const_blocks/cmake_lists.cc
+++ b/mindspore/lite/micro/coder/generator/component/const_blocks/cmake_lists.cc
@@ -34,6 +34,8 @@ set(HEADER_PATH ${PKG_PATH}/inference)
 option(MICRO_BUILD_ARM64 "build android arm64" OFF)
 option(MICRO_BUILD_ARM32A "build android arm32" OFF)
 
+add_compile_definitions(NOT_USE_STL)
+
 if(MICRO_BUILD_ARM64 OR MICRO_BUILD_ARM32A)
   add_compile_definitions(ENABLE_NEON)
   add_compile_definitions(ENABLE_ARM)
@@ -95,6 +97,8 @@ set(HEADER_PATH ${PKG_PATH}/inference)
 message("operator lib path: ${OP_LIB}")
 message("operator header path: ${OP_HEADER_PATH}")
 
+add_compile_definitions(NOT_USE_STL)
+
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/../include)
 include_directories(${OP_HEADER_PATH})
 include_directories(${HEADER_PATH})
diff --git a/mindspore/lite/micro/coder/generator/component/const_blocks/msession.cc b/mindspore/lite/micro/coder/generator/component/const_blocks/msession.cc
index eb9acef8a30..f158b179ee7 100644
--- a/mindspore/lite/micro/coder/generator/component/const_blocks/msession.cc
+++ b/mindspore/lite/micro/coder/generator/component/const_blocks/msession.cc
@@ -63,31 +63,25 @@ class LiteSession : public session::LiteSession {
 
   int CompileGraph(lite::Model *model) override;
 
-  std::vector<tensor::MSTensor *> GetInputs() const override;
+  Vector<tensor::MSTensor *> GetInputs() const override;
 
-  mindspore::tensor::MSTensor *GetInputsByTensorName(const std::string &tensor_name) const override { return nullptr; }
+  mindspore::tensor::MSTensor *GetInputsByTensorName(const String &tensor_name) const override { return nullptr; }
 
   int RunGraph(const KernelCallBack &before = nullptr, const KernelCallBack &after = nullptr) override;
 
-  std::vector<tensor::MSTensor *> GetOutputsByNodeName(const std::string &node_name) const override;
+  Vector<tensor::MSTensor *> GetOutputsByNodeName(const String &node_name) const override;
 
-  std::unordered_map<std::string, mindspore::tensor::MSTensor *> GetOutputs() const override;
+  Vector<String> GetOutputTensorNames() const override;
 
-  std::vector<std::string> GetOutputTensorNames() const override;
+  mindspore::tensor::MSTensor *GetOutputByTensorName(const String &tensor_name) const override;
 
-  mindspore::tensor::MSTensor *GetOutputByTensorName(const std::string &tensor_name) const override;
-
-  int Resize(const std::vector<tensor::MSTensor *> &inputs, const std::vector<std::vector<int>> &dims) override;
+  int Resize(const Vector<tensor::MSTensor *> &inputs, const Vector<Vector<int>> &dims) override { return RET_ERROR; }
 
   int InitRuntimeBuffer();
 
  private:
-  int SetInputsData(const std::vector<MTensor *> &inputs) const;
-  std::vector<MTensor *> inputs_;
-  std::vector<MTensor *> outputs_;
-  std::unordered_map<std::string, mindspore::tensor::MSTensor *> output_tensor_map_;
-  std::unordered_map<std::string, std::vector<mindspore::tensor::MSTensor *>> output_node_map_;
-
+  Vector<MTensor *> inputs_;
+  Vector<MTensor *> outputs_;
   void *runtime_buffer_;
 };
 
@@ -95,7 +89,6 @@ class LiteSession : public session::LiteSession {
 }  // namespace mindspore
 
 #endif  // MINDSPORE_LITE_MICRO_LIBRARY_SOURCE_SESSION_H_
-
 )RAW";
 
 const char *session_source = R"RAW(
@@ -130,8 +123,7 @@ LiteSession::~LiteSession() {
     delete input;
     input = nullptr;
   }
-  for (auto &item : output_tensor_map_) {
-    auto output = item.second;
+  for (auto &output : outputs_) {
     if (output == nullptr) {
       continue;
     }
@@ -153,46 +145,28 @@ int LiteSession::InitRuntimeBuffer() {
   return RET_OK;
 }
 
-std::vector<tensor::MSTensor *> LiteSession::GetInputs() const {
-  std::vector<tensor::MSTensor *> inputs;
-  inputs.insert(inputs.begin(), inputs_.begin(), inputs_.end());
+Vector<tensor::MSTensor *> LiteSession::GetInputs() const {
+  Vector<tensor::MSTensor *> inputs;
+  for (const auto &input : inputs_) {
+    inputs.push_back(input);
+  }
   return inputs;
 }
 
-std::vector<tensor::MSTensor *> LiteSession::GetOutputsByNodeName(const std::string &node_name) const {
-  auto iter = output_node_map_.find(node_name);
-  if (iter == output_node_map_.end()) {
-    std::vector<tensor::MSTensor *> empty;
-    return empty;
-  }
-  return iter->second;
+Vector<tensor::MSTensor *> LiteSession::GetOutputsByNodeName(const String &node_name) const {
+  Vector<tensor::MSTensor *> outputs;
+  return outputs;
 }
 
-std::unordered_map<std::string, mindspore::tensor::MSTensor *> LiteSession::GetOutputs() const {
-  return output_tensor_map_;
-}
-
-std::vector<std::string> LiteSession::GetOutputTensorNames() const {
-  std::vector<std::string> output_names;
-  for (const auto &item : output_node_map_) {
-    for (const auto &output : item.second) {
-      output_names.emplace_back(output->tensor_name());
-    }
+Vector<String> LiteSession::GetOutputTensorNames() const {
+  Vector<String> output_names;
+  for (const auto &output : outputs_) {
+    output_names.push_back(output->tensor_name());
   }
   return output_names;
 }
 
-mindspore::tensor::MSTensor *LiteSession::GetOutputByTensorName(const std::string &tensor_name) const {
-  auto item = output_tensor_map_.find(tensor_name);
-  if (item == output_tensor_map_.end()) {
-    return nullptr;
-  }
-  return item->second;
-}
-
-int LiteSession::Resize(const std::vector<tensor::MSTensor *> &inputs, const std::vector<std::vector<int>> &dims) {
-  return RET_OK;
-}
+mindspore::tensor::MSTensor *LiteSession::GetOutputByTensorName(const String &tensor_name) const { return nullptr; }
 
 }  // namespace lite
 
@@ -219,7 +193,6 @@ session::LiteSession *session::LiteSession::CreateSession(const char *net_buf, s
   return session;
 }
 }  // namespace mindspore
-
 )RAW";
 
 }  // namespace mindspore::lite::micro
diff --git a/mindspore/lite/micro/coder/generator/component/const_blocks/mtensor.cc b/mindspore/lite/micro/coder/generator/component/const_blocks/mtensor.cc
index d59b860b234..2e8e1f15b0f 100644
--- a/mindspore/lite/micro/coder/generator/component/const_blocks/mtensor.cc
+++ b/mindspore/lite/micro/coder/generator/component/const_blocks/mtensor.cc
@@ -19,7 +19,6 @@
 namespace mindspore::lite::micro {
 
 const char *tensor_header = R"RAW(
-
 /**
  * Copyright 2021 Huawei Technologies Co., Ltd
  *
@@ -40,8 +39,6 @@ const char *tensor_header = R"RAW(
 #define MINDSPORE_LITE_MICRO_LIBRARY_SOURCE_TENSOR_H_
 
 #include "include/ms_tensor.h"
-#include <utility>
-#include <vector>
 
 namespace mindspore {
 namespace lite {
@@ -51,7 +48,7 @@ struct QuantArg {
   float var_corr{1};
   float mean_corr{0};
   bool inited;
-  std::vector<float> clusters{};
+  Vector<float> clusters{};
   int bitNum;
   int roundType;
   int multiplier;
@@ -61,38 +58,35 @@ struct QuantArg {
 class MTensor : public mindspore::tensor::MSTensor {
  public:
   MTensor() = default;
-  MTensor(std::string name, enum TypeId type, std::vector<int32_t> shape)
-      : tensor_name_(std::move(name)), data_type_(type), shape_(std::move(shape)) {}
+  MTensor(String name, TypeId type, Vector<int32_t> shape) : tensor_name_(name), data_type_(type), shape_(shape) {}
   ~MTensor() override;
 
   TypeId data_type() const override { return data_type_; }
-  std::vector<int> shape() const override { return shape_; }
-  int DimensionSize(size_t index) const override;
+  Vector<int> shape() const override { return shape_; }
+  void set_shape(const Vector<int> &shape) override { shape_ = shape; }
   int ElementsNum() const override;
   size_t Size() const override;
+  String tensor_name() const override { return tensor_name_; }
+  void set_tensor_name(const String name) override { tensor_name_ = name; }
   void *MutableData() override;
-  std::string tensor_name() const override { return tensor_name_; }
-  void set_tensor_name(const std::string name) override { tensor_name_ = name; }
+  void *data() override { return data_; }
   void set_data(void *data) override { data_ = data; }
 
  private:
-  std::string tensor_name_;
+  String tensor_name_;
   TypeId data_type_;
-  std::vector<int> shape_;
+  Vector<int> shape_;
   void *data_ = nullptr;
-  std::vector<QuantArg> quant_params_;
+  Vector<QuantArg> quant_params_;
 };
 
 }  // namespace lite
 }  // namespace mindspore
 
 #endif  // MINDSPORE_LITE_MICRO_LIBRARY_SOURCE_TENSOR_H_
-
-
 )RAW";
 
 const char *tensor_source = R"RAW(
-
 /**
  * Copyright 2021 Huawei Technologies Co., Ltd
  *
@@ -154,14 +148,6 @@ MTensor::~MTensor() {
   }
 }
 
-int MTensor::DimensionSize(const size_t index) const {
-  int dim_size = -1;
-  if (index < shape_.size()) {
-    dim_size = shape_[index];
-  }
-  return dim_size;
-}
-
 int MTensor::ElementsNum() const {
   int elements = 1;
   for (int i : shape_) {
@@ -183,7 +169,6 @@ void *MTensor::MutableData() {
 }
 }  // namespace lite
 }  // namespace mindspore
-
 )RAW";
 
 }  // namespace mindspore::lite::micro
diff --git a/mindspore/lite/micro/coder/generator/generator.cc b/mindspore/lite/micro/coder/generator/generator.cc
index 6fc56205c13..1ad60bc5750 100644
--- a/mindspore/lite/micro/coder/generator/generator.cc
+++ b/mindspore/lite/micro/coder/generator/generator.cc
@@ -111,6 +111,7 @@ int Generator::CodeSessionImplement() {
   ofs << g_hwLicense;
   ofs << "#include \"session.h\"\n";
   ofs << "#include \"net.h\"\n\n";
+  ofs << "#include <new>\n\n";
   CodeSessionCompileGraph(ofs, ctx_);
   ofs << session_source;
   return RET_OK;
diff --git a/mindspore/lite/micro/coder/operator_library/CMakeLists.txt b/mindspore/lite/micro/coder/operator_library/CMakeLists.txt
index ff0b529c16e..984890590a8 100644
--- a/mindspore/lite/micro/coder/operator_library/CMakeLists.txt
+++ b/mindspore/lite/micro/coder/operator_library/CMakeLists.txt
@@ -60,4 +60,5 @@ endif()
 
 # generate static library
 add_library(ops STATIC ${OP_FILES})
+target_compile_definitions(ops PRIVATE NOT_USE_STL)
 install(TARGETS ops ARCHIVE DESTINATION ${LIB_PATH})
diff --git a/mindspore/lite/src/common/string.cc b/mindspore/lite/src/common/string.cc
new file mode 100644
index 00000000000..881a3a4b170
--- /dev/null
+++ b/mindspore/lite/src/common/string.cc
@@ -0,0 +1,300 @@
+/**
+ * Copyright 2021 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifdef NOT_USE_STL
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <float.h>
+#include <stdint.h>
+#include "include/lite_utils.h"
+
+namespace mindspore {
+String::String() {
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * 1));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  buffer_[0] = '\0';
+  size_ = 0;
+}
+
+String::String(size_t count, char ch) {
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (count + 1)));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  memset(buffer_, ch, count);
+  buffer_[count] = '\0';
+  size_ = count;
+}
+String::String(const char *s, size_t count) {
+  if (s == nullptr) {
+    buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * 1));
+    if (buffer_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    buffer_[0] = '\0';
+    size_ = 0;
+    return;
+  }
+  size_t size_s = strlen(s);
+  if (size_s <= count) {
+    size_ = size_s;
+  } else {
+    size_ = count;
+  }
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (size_ + 1)));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  strncpy(buffer_, s, size_);
+  buffer_[size_] = '\0';
+}
+
+String::String(const char *s) {
+  if (s == nullptr) {
+    buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * 1));
+    if (buffer_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    buffer_[0] = '\0';
+    size_ = 0;
+    return;
+  }
+  size_ = strlen(s);
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (size_ + 1)));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  memcpy(buffer_, s, size_ + 1);
+}
+
+String::String(const String &other) {
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (other.size_ + 1)));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  size_ = other.size_;
+  memcpy(buffer_, other.buffer_, size_ + 1);
+}
+
+String::String(const String &other, size_t pos, size_t count) {
+  if (pos >= other.size_) {
+    buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * 1));
+    if (buffer_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    buffer_[0] = '\0';
+    size_ = 0;
+  } else {
+    if (count == npos) {
+      count = other.size_ - pos;
+    }
+    if (pos + count > other.size_) {
+      size_ = other.size_ - pos;
+    } else {
+      size_ = count;
+    }
+    buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (size_ + 1)));
+    if (buffer_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    strncpy(buffer_, other.buffer_ + pos, size_);
+    buffer_[size_] = '\0';
+  }
+}
+
+String::~String() { free(buffer_); }
+
+String &String::operator=(const String &str) {
+  if (this == &str) {
+    return *this;
+  }
+  free(buffer_);
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (str.size_ + 1)));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  size_ = str.size_;
+  memcpy(buffer_, str.buffer_, size_ + 1);
+  return *this;
+}
+
+String &String::operator=(const char *str) {
+  free(buffer_);
+  if (str == nullptr) {
+    buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * 1));
+    if (buffer_ == nullptr) {
+      MS_C_EXCEPTION("malloc data failed");
+    }
+    buffer_[0] = '\0';
+    size_ = 0;
+    return *this;
+  }
+  size_t size_s = strlen(str);
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * (size_s + 1)));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  size_ = size_s;
+  memcpy(buffer_, str, size_ + 1);
+  return *this;
+}
+
+char &String::at(size_t pos) {
+  if (pos >= size_) {
+    MS_C_EXCEPTION("pos out of range");
+  }
+  return buffer_[pos];
+}
+const char &String::at(size_t pos) const {
+  if (pos >= size_) {
+    MS_C_EXCEPTION("pos out of range");
+  }
+  return buffer_[pos];
+}
+char &String::operator[](size_t pos) {
+  if (pos >= size_) {
+    MS_C_EXCEPTION("pos out of range");
+  }
+  return this->at(pos);
+}
+const char &String::operator[](size_t pos) const {
+  if (pos >= size_) {
+    MS_C_EXCEPTION("pos out of range");
+  }
+  return this->at(pos);
+}
+char *String::data() noexcept { return buffer_; };
+const char *String::data() const noexcept { return buffer_; }
+const char *String::c_str() const noexcept { return buffer_; }
+
+// capacity
+bool String::empty() const noexcept { return size_ == 0; }
+size_t String::size() const noexcept { return size_; }
+size_t String::length() const noexcept { return size_; }
+
+// operations
+void String::clear() noexcept {
+  free(buffer_);
+  buffer_ = reinterpret_cast<char *>(malloc(sizeof(char) * 1));
+  if (buffer_ == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  buffer_[0] = '\0';
+  size_ = 0;
+}
+
+String &String::operator+(const String &str) {
+  (*this) += str;
+  return *this;
+}
+
+String &String::operator+=(const String &str) {
+  size_t new_size = size_ + str.size_;
+  char *tmp = reinterpret_cast<char *>(malloc(sizeof(char) * (new_size + 1)));
+  if (tmp == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  memcpy(tmp, this->buffer_, size_ + 1);
+  strncat(tmp, str.buffer_, str.size_);
+  tmp[new_size] = '\0';
+  free(buffer_);
+  buffer_ = tmp;
+  size_ = new_size;
+  return *this;
+}
+
+String &String::operator+=(const char *str) {
+  if (str == nullptr) {
+    return *this;
+  }
+  size_t str_size = strlen(str);
+  size_t new_size = size_ + str_size;
+  char *tmp = reinterpret_cast<char *>(malloc(sizeof(char) * (new_size + 1)));
+  if (tmp == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  memcpy(tmp, this->buffer_, size_ + 1);
+  strncat(tmp, str, str_size);
+  tmp[new_size] = '\0';
+  free(buffer_);
+  buffer_ = tmp;
+  size_ = new_size;
+  return *this;
+}
+
+String &String::operator+=(const char ch) {
+  char *tmp = reinterpret_cast<char *>(malloc(sizeof(char) * (size_ + 2)));
+  if (tmp == nullptr) {
+    MS_C_EXCEPTION("malloc data failed");
+  }
+  memcpy(tmp, this->buffer_, size_ + 1);
+  tmp[size_] = ch;
+  tmp[size_ + 1] = '\0';
+  free(buffer_);
+  buffer_ = tmp;
+  size_ += 1;
+  return *this;
+}
+
+String &String::append(size_t count, const char ch) {
+  (*this) += ch;
+  return *this;
+}
+String &String::append(const String &str) {
+  (*this) += str;
+  return *this;
+}
+String &String::append(const char *str) {
+  if (str == nullptr) {
+    return *this;
+  }
+  (*this) += str;
+  return *this;
+}
+
+int String::compare(const String &str) const { return strcmp(buffer_, str.buffer_); }
+int String::compare(const char *str) const { return strcmp(buffer_, str); }
+
+String String::substr(size_t pos, size_t count) const { return String(*this, pos, count); }
+
+String operator+(const String &str1, const char *str2) {
+  String str = str1;
+  str += str2;
+  return str;
+}
+
+String operator+(const char *str1, const String &str2) {
+  String str = str2;
+  str += str1;
+  return str;
+}
+
+String to_String(int32_t value) {
+  char tmp[sizeof(int32_t) * 4];
+  snprintf(tmp, sizeof(int32_t) * 4, "%d", value);
+  return String(tmp, strlen(tmp));
+}
+
+String to_String(float value) {
+  char tmp[FLT_MAX_10_EXP + 20];
+  snprintf(tmp, FLT_MAX_10_EXP + 20, "%f", value);
+  return String(tmp, strlen(tmp));
+}
+}  // namespace mindspore
+#endif  // NOT_USE_STL