diff --git a/paddle/fluid/imperative/amp_auto_cast.cc b/paddle/fluid/imperative/amp_auto_cast.cc
index 48e5e430b136a530822c5be88f6ccc6302e0ea85..b0d86f6db9f960bc9b5e4c8d06ce368b6cfb4f1f 100644
--- a/paddle/fluid/imperative/amp_auto_cast.cc
+++ b/paddle/fluid/imperative/amp_auto_cast.cc
@@ -24,6 +24,17 @@ namespace imperative {
 
 class VarBase;
 
+AutoCastGuard::AutoCastGuard(std::shared_ptr<Tracer> tracer, AmpLevel level)
+    : tracer_(tracer) {
+  pre_amp_level_ = tracer_->GetAmpLevel();
+
+  if (pre_amp_level_ != level) {
+    tracer_->SetAmpLevel(level);
+  }
+}
+
+AutoCastGuard::~AutoCastGuard() { tracer_->SetAmpLevel(pre_amp_level_); }
+
 AmpOperators::AmpOperators()
     : allow_ops_(new std::unordered_set<std::string>()),
       block_ops_(new std::unordered_set<std::string>()),
@@ -117,7 +128,7 @@ static inline std::shared_ptr<imperative::VarBase> CastToType(
   imperative::NameVarBaseMap outs = {{"Out", {out}}};
 
   {
-    AutoCastGuard guard(tracer, 0);
+    AutoCastGuard guard(tracer, AmpLevel::O0);
     tracer->TraceOp("cast", ins, outs, std::move(attrs));
   }
 
diff --git a/paddle/fluid/imperative/amp_auto_cast.h b/paddle/fluid/imperative/amp_auto_cast.h
index 79bc83a777aa906562d4f85ae1ee71e7152a2496..903e2652888d8502ba22c54dcbf3872171e2ba84 100644
--- a/paddle/fluid/imperative/amp_auto_cast.h
+++ b/paddle/fluid/imperative/amp_auto_cast.h
@@ -19,15 +19,22 @@
 #include <tuple>
 #include <unordered_set>
 
-#include "paddle/fluid/imperative/tracer.h"
 #include "paddle/fluid/imperative/type_defs.h"
 
 namespace paddle {
 namespace imperative {
 
-// Singleton implementation with C++ 11
+// NOTE(zhiqiu): only O1 and O2 are valid now
+enum class AmpLevel {
+  O0 = 0,  // fp32
+  O1,      // amp, mixed fp32-fp16
+  O2,      // almost fp16
+  O3,      // fp16
+};
+
 class Tracer;
 
+// Singleton implementation with C++ 11
 class AmpOperators {
  public:
   ~AmpOperators();
@@ -63,16 +70,9 @@ std::ostream& operator<<(std::ostream& os, AmpOperators& ops);
 // NOTE(zhiqiu): AutoCastGuard is used for RAII.
 class AutoCastGuard {
  public:
-  AutoCastGuard(std::shared_ptr<Tracer> tracer, int guard_level)
-      : tracer_(tracer) {
-    pre_amp_level_ = tracer_->AMPLevel();
-
-    if (pre_amp_level_ != guard_level) {
-      tracer_->SetAMPLevel(guard_level);
-    }
-  }
+  AutoCastGuard(std::shared_ptr<Tracer> tracer, AmpLevel guard_level);
 
-  ~AutoCastGuard() { tracer_->SetAMPLevel(pre_amp_level_); }
+  ~AutoCastGuard();
 
   // forbid copy and operator=
   AutoCastGuard(const AutoCastGuard& guard) = delete;
@@ -80,7 +80,7 @@ class AutoCastGuard {
 
  private:
   std::shared_ptr<Tracer> tracer_;
-  int pre_amp_level_;
+  AmpLevel pre_amp_level_;
 };
 
 NameVarBaseMap AutoCastInputs(const std::string& op_type,
diff --git a/paddle/fluid/imperative/tracer.cc b/paddle/fluid/imperative/tracer.cc
index 49e079c58caf3c7756664554d466d3900fbbae4d..0f363d0ea1bff87c05c15912134e9c01bada521e 100644
--- a/paddle/fluid/imperative/tracer.cc
+++ b/paddle/fluid/imperative/tracer.cc
@@ -176,10 +176,10 @@ void Tracer::TraceOp(const std::string& type, const NameVarBaseMap& ins,
                               : attr_checker->GetDefaultAttrMap();
 
   NameVarBaseMap new_ins = ins;
-  if (amp_level_ == 1) {
+  if (amp_level_ == AmpLevel::O1) {
     VLOG(5) << "Auto mixed precision run operator: " << type;
     new_ins = AutoCastInputs(type, ins);
-  } else if (amp_level_ == 2) {
+  } else if (amp_level_ == AmpLevel::O2) {
     VLOG(5) << "Pure fp16 run operator: " << type;
     new_ins = CastPureFp16Inputs(type, ins);
   }
diff --git a/paddle/fluid/imperative/tracer.h b/paddle/fluid/imperative/tracer.h
index e77623d7a4609295ba6ff140e9aef7539debbd03..418b2069b5bb62dfcd7a2eb9aa3829d14e22c6f9 100644
--- a/paddle/fluid/imperative/tracer.h
+++ b/paddle/fluid/imperative/tracer.h
@@ -23,6 +23,7 @@
 #include <vector>
 #include "ThreadPool.h"
 #include "paddle/fluid/framework/garbage_collector.h"
+#include "paddle/fluid/imperative/amp_auto_cast.h"
 #include "paddle/fluid/imperative/basic_engine.h"
 #include "paddle/fluid/imperative/jit/program_desc_tracer.h"
 #include "paddle/fluid/imperative/layer.h"
@@ -31,6 +32,8 @@
 namespace paddle {
 namespace imperative {
 
+enum class AmpLevel;
+
 using GarbageCollectorMap =
     std::map<platform::Place,
              std::unique_ptr<paddle::framework::GarbageCollector>>;
@@ -105,9 +108,9 @@ class Tracer {
 
   void SetHasGrad(bool has_grad) { has_grad_ = has_grad; }
 
-  void SetAMPLevel(int level) { amp_level_ = level; }
+  void SetAmpLevel(AmpLevel level) { amp_level_ = level; }
 
-  int AMPLevel() const { return amp_level_; }
+  AmpLevel GetAmpLevel() const { return amp_level_; }
 
   paddle::framework::GarbageCollector* MutableGarbageCollectorIfNotExists(
       const platform::Place& place);
@@ -120,7 +123,7 @@ class Tracer {
   platform::Place expected_place_;
   GarbageCollectorMap gcs_;
   static thread_local bool has_grad_;
-  int amp_level_{0};
+  AmpLevel amp_level_{AmpLevel::O0};
 };
 
 // To access static variable current_tracer
diff --git a/paddle/fluid/pybind/imperative.cc b/paddle/fluid/pybind/imperative.cc
index db84c1142ae23056e03825486e9970deb2d1a70e..f94afaa56b8dfd178cbdf042a6fa05557532d777 100644
--- a/paddle/fluid/pybind/imperative.cc
+++ b/paddle/fluid/pybind/imperative.cc
@@ -1940,6 +1940,13 @@ void BindImperative(py::module *m_ptr) {
            &imperative::jit::ProgramDescTracer::CreateProgramDesc)
       .def("reset", &imperative::jit::ProgramDescTracer::Reset);
 
+  py::enum_<paddle::imperative::AmpLevel>(m, "AmpLevel", py::arithmetic())
+      .value("O0", paddle::imperative::AmpLevel::O0)
+      .value("O1", paddle::imperative::AmpLevel::O1)
+      .value("O2", paddle::imperative::AmpLevel::O2)
+      .value("O3", paddle::imperative::AmpLevel::O3)
+      .export_values();
+
   py::class_<imperative::Tracer, std::shared_ptr<imperative::Tracer>>(
       m, "Tracer", R"DOC()DOC")
       .def("__init__",
@@ -1947,8 +1954,8 @@ void BindImperative(py::module *m_ptr) {
       .def_property("_enable_program_desc_tracing",
                     &imperative::Tracer::IsProgramDescTracingEnabled,
                     &imperative::Tracer::SetEnableProgramDescTracing)
-      .def_property("_amp_level", &imperative::Tracer::AMPLevel,
-                    &imperative::Tracer::SetAMPLevel)
+      .def_property("_amp_level", &imperative::Tracer::GetAmpLevel,
+                    &imperative::Tracer::SetAmpLevel)
       .def_property("_has_grad", &imperative::Tracer::HasGrad,
                     &imperative::Tracer::SetHasGrad)
       .def_property(
diff --git a/python/paddle/distributed/fleet/meta_parallel/pp_utils/utils.py b/python/paddle/distributed/fleet/meta_parallel/pp_utils/utils.py
index b29b0b3e2755740c0d0bb5f5ba98acf5149cf168..08266096548c4a2718b29e013513ce2bac6a79ef 100644
--- a/python/paddle/distributed/fleet/meta_parallel/pp_utils/utils.py
+++ b/python/paddle/distributed/fleet/meta_parallel/pp_utils/utils.py
@@ -198,7 +198,7 @@ class _HPRecomputeFunction(PyLayer):
 
         # TODO support AMP
         tracer = framework._dygraph_tracer()
-        if tracer._amp_level == 0:
+        if tracer._amp_level == core.AmpLevel.O0:
             ctx.is_fw_autocast = False
         else:
             ctx.is_fw_autocast = True
diff --git a/python/paddle/distributed/fleet/utils/recompute.py b/python/paddle/distributed/fleet/utils/recompute.py
index 302877e51fe01da58c033eee53942fd29342c704..56a64049b16e1553fada8e1e3b36fec75577e3a7 100755
--- a/python/paddle/distributed/fleet/utils/recompute.py
+++ b/python/paddle/distributed/fleet/utils/recompute.py
@@ -98,7 +98,7 @@ class RecomputeFunction(PyLayer):
 
         # TODO support AMP
         tracer = framework._dygraph_tracer()
-        if tracer._amp_level == 0:
+        if tracer._amp_level == core.AmpLevel.O0:
             ctx.is_fw_autocast = False
         else:
             ctx.is_fw_autocast = True
diff --git a/python/paddle/fluid/dygraph/amp/auto_cast.py b/python/paddle/fluid/dygraph/amp/auto_cast.py
index 0d02a383c1bb80eb6786bbe183690986c1566d56..d218e6b7490d9ca13a955f4a95612c41fe0f9d00 100644
--- a/python/paddle/fluid/dygraph/amp/auto_cast.py
+++ b/python/paddle/fluid/dygraph/amp/auto_cast.py
@@ -24,6 +24,8 @@ import paddle
 import operator
 import types
 
+AMP_LEVEL = core.AmpLevel
+
 __all__ = ['amp_guard', 'amp_decorate']
 
 # The set of ops that support fp16 calculation and are considered numerically-
@@ -108,7 +110,7 @@ def _in_amp_guard():
     """
     tracer = _dygraph_tracer()
     if tracer:
-        if tracer._amp_level == 1:
+        if tracer._amp_level == core.AmpLevel.O1:
             return True
         else:
             return False
@@ -251,11 +253,11 @@ def amp_guard(enable=True,
         enable = False
 
     if level == 'O1':
-        amp_level = 1
+        amp_level = AMP_LEVEL.O1
         _white_list = WHITE_LIST
         _black_list = BLACK_LIST
     else:
-        amp_level = 2
+        amp_level = AMP_LEVEL.O2
         _white_list = PURE_FP16_WHITE_LIST
         _black_list = PURE_FP16_BLACK_LIST
 
@@ -264,7 +266,7 @@ def amp_guard(enable=True,
                                                 custom_black_list, level)
 
     if not enable:
-        amp_level = 0
+        amp_level = AMP_LEVEL.O0
 
     if tracer:
         # enable auto_cast