diff --git a/paddle/framework/operator.cc b/paddle/framework/operator.cc
index 9bf60b7b11636df97031d111031ef782a173006b..c08c6bba592fb490cc033ed22698b238b9b5477c 100644
--- a/paddle/framework/operator.cc
+++ b/paddle/framework/operator.cc
@@ -52,7 +52,8 @@ std::vector<std::string> OperatorBase::Inputs(const std::string& name) const {
   PADDLE_ENFORCE(in_out_idxs_ != nullptr, "IO Idx could not be nullptr");
   auto input_format = GetAttr<std::vector<int>>("input_format");
   auto offset = in_out_idxs_->at(name);
-  PADDLE_ENFORCE(input_format.at((size_t)offset + 1) <= inputs_.size(),
+  PADDLE_ENFORCE(input_format.at(static_cast<size_t>(offset) + 1) <=
+                     static_cast<int>(inputs_.size()),
                  "Input Out Of Range");
 
   return std::vector<std::string>{
@@ -78,7 +79,8 @@ std::vector<std::string> OperatorBase::Outputs(const std::string& name) const {
   PADDLE_ENFORCE(in_out_idxs_ != nullptr, "InOut Indice could not be nullptr");
   auto output_format = GetAttr<std::vector<int>>("output_format");
   auto offset = in_out_idxs_->at(name);
-  PADDLE_ENFORCE(output_format.at((size_t)offset + 1) <= outputs_.size(),
+  PADDLE_ENFORCE(output_format.at(static_cast<size_t>(offset) + 1) <=
+                     static_cast<int>(outputs_.size()),
                  "Output Out of Range");
   return std::vector<std::string>{
       outputs_.begin() + output_format.at(offset),
diff --git a/paddle/framework/operator.h b/paddle/framework/operator.h
index ef1521b83bb50774d7b4f710a5deff879373ba35..ff518265a45382115b53d61cab52b85a73de5f70 100644
--- a/paddle/framework/operator.h
+++ b/paddle/framework/operator.h
@@ -108,11 +108,11 @@ class OperatorContext {
 
   size_t OutputSize() const { return op_.outputs_.size(); }
 
-  const Variable* InputVar(const size_t& index) const {
+  const Variable* InputVar(const size_t index) const {
     return scope_->GetVariable(op_.inputs_.at(index));
   }
 
-  Variable* OutputVar(const size_t& index) const {
+  Variable* OutputVar(const size_t index) const {
     return scope_->GetVariable(op_.outputs_.at(index));
   }
 
@@ -146,23 +146,31 @@ class OperatorContext {
   }
 
   template <typename T>
-  const T* Input(const size_t& index) const {
-    return &(InputVar(index)->Get<T>());
+  const T* Input(const size_t index) const {
+    auto var = InputVar(index);
+    PADDLE_ENFORCE(var != nullptr, "Input(%d) should not be nullptr", index);
+    return &var->Get<T>();
   }
 
   template <typename T>
-  T* Output(const size_t& index) const {
-    return OutputVar(index)->GetMutable<T>();
+  T* Output(const size_t index) const {
+    auto var = OutputVar(index);
+    PADDLE_ENFORCE(var != nullptr, "Output(%d) should not be nullptr", index);
+    return var->GetMutable<T>();
   }
 
   template <typename T>
   const T* Input(const std::string& name) const {
-    return &(InputVar(name)->Get<T>());
+    auto var = InputVar(name);
+    PADDLE_ENFORCE(var != nullptr, "Input(%s) should not be nullptr", name);
+    return &var->Get<T>();
   }
 
   template <typename T>
   T* Output(const std::string& name) const {
-    return OutputVar(name)->GetMutable<T>();
+    auto var = OutputVar(name);
+    PADDLE_ENFORCE(var != nullptr, "Output(%s) should not be nullptr", name);
+    return var->GetMutable<T>();
   }
 
   template <typename T>
@@ -171,8 +179,12 @@ class OperatorContext {
     std::vector<const T*> res;
     res.reserve(names.size());
     std::transform(names.begin(), names.end(), std::back_inserter(res),
-                   [this](const std::string& name) {
-                     return &scope_->GetVariable(name)->Get<T>();
+                   [&](const std::string& sub_name) {
+                     auto var = scope_->GetVariable(sub_name);
+                     PADDLE_ENFORCE(var != nullptr,
+                                    "MultiInput(%s:%s) should not be nullptr",
+                                    name, sub_name);
+                     return &var->Get<T>();
                    });
     return res;
   }
@@ -183,8 +195,12 @@ class OperatorContext {
     std::vector<const T*> res;
     res.reserve(names.size());
     std::transform(names.begin(), names.end(), std::back_inserter(res),
-                   [this](const std::string& name) {
-                     return scope_->GetVariable(name)->GetMutable<T>();
+                   [&](const std::string& sub_name) {
+                     auto var = scope_->GetVariable(sub_name);
+                     PADDLE_ENFORCE(var != nullptr,
+                                    "MultiOutput(%s:%s) should not be nullptr",
+                                    name, sub_name);
+                     return var->GetMutable<T>();
                    });
     return res;
   }