diff --git a/paddle/fluid/framework/no_need_buffer_vars_inference.h b/paddle/fluid/framework/no_need_buffer_vars_inference.h
index 2c933659840d02e65c3b222144a31e558e8e8ae8..a63575611bced370d04b3847c7eb3500cb37bad8 100644
--- a/paddle/fluid/framework/no_need_buffer_vars_inference.h
+++ b/paddle/fluid/framework/no_need_buffer_vars_inference.h
@@ -45,15 +45,16 @@ class NoNeedBufferVarsInference {
   const AttributeMap &attrs_;
 };
 
-#define DECLARE_NO_NEED_BUFFER_VARS_INFERENCE(class_type, ...)               \
-  class class_type : public ::paddle::framework::NoNeedBufferVarsInference { \
-   public:                                                                   \
-    using ::paddle::framework::NoNeedBufferVarsInference::                   \
-        NoNeedBufferVarsInference;                                           \
-                                                                             \
-    std::unordered_set<std::string> operator()() const override {            \
-      return {__VA_ARGS__};                                                  \
-    }                                                                        \
+#define DECLARE_NO_NEED_BUFFER_VARS_INFERENCE(class_type, ...)  \
+  class class_type final                                        \
+      : public ::paddle::framework::NoNeedBufferVarsInference { \
+   public:                                                      \
+    using ::paddle::framework::NoNeedBufferVarsInference::      \
+        NoNeedBufferVarsInference;                              \
+                                                                \
+    std::unordered_set<std::string> operator()() const final {  \
+      return {__VA_ARGS__};                                     \
+    }                                                           \
   }
 
 }  // namespace framework
diff --git a/paddle/fluid/operators/assign_op.cc b/paddle/fluid/operators/assign_op.cc
index 871dfe67343dbe58296095e1df8668e0ebd11d45..ff423778c5982c31a5ff5b0a0e264750ad81ed04 100644
--- a/paddle/fluid/operators/assign_op.cc
+++ b/paddle/fluid/operators/assign_op.cc
@@ -144,12 +144,14 @@ class AssignGradMaker : public framework::SingleGradOpDescMaker {
   }
 };
 
+DECLARE_INPLACE_OP_INFERER(AssignOpInplaceInferer, {"X", "Out"});
+
 }  // namespace operators
 }  // namespace paddle
 
 namespace ops = paddle::operators;
 REGISTER_OPERATOR(assign, ops::AssignOp, ops::AssignGradMaker,
-                  ops::AssignOpProtoMaker);
+                  ops::AssignOpProtoMaker, ops::AssignOpInplaceInferer);
 REGISTER_OP_CPU_KERNEL_FUNCTOR(assign, float, ops::AssignKernel, double,
                                ops::AssignKernel, int, ops::AssignKernel,
                                int64_t, ops::AssignKernel);