diff --git a/paddle/fluid/framework/operator.cc b/paddle/fluid/framework/operator.cc
index 14fcde2fe3b1c3acfc0994e9cd37a784c57826d7..9259bb740a8a2408e4dc7be21711560fdf250752 100644
--- a/paddle/fluid/framework/operator.cc
+++ b/paddle/fluid/framework/operator.cc
@@ -358,7 +358,7 @@ static bool VarIsTensor(const Variable* var) {
   return var->IsType<LoDTensor>() || var->IsType<SelectedRows>();
 }
 
-static const Tensor* GetTensorFromVar(Variable* var) {
+const Tensor* GetTensorFromVar(Variable* var) {
   if (var->IsType<LoDTensor>()) {
     return var->GetMutable<LoDTensor>();
   } else if (var->IsType<SelectedRows>()) {
diff --git a/paddle/fluid/framework/operator.h b/paddle/fluid/framework/operator.h
index 626b50edfd39424473be33e9f8baec5970471477..a04d2834eb94c2d8df9c6e48782d10bb3254a6dd 100644
--- a/paddle/fluid/framework/operator.h
+++ b/paddle/fluid/framework/operator.h
@@ -63,6 +63,7 @@ inline std::string GradVarName(const std::string& var_name) {
 }
 
 proto::VarType::Type GetDataTypeOfVar(const Variable* var);
+const Tensor* GetTensorFromVar(Variable* var);
 
 class OperatorBase;
 class ExecutionContext;
diff --git a/paddle/fluid/operators/sum_op.cc b/paddle/fluid/operators/sum_op.cc
index cc3d8db3b5a34435332bbad19e2cab1447e9e0b9..6fe30630e9683f59044b216b9e9b1f7dd647b1e2 100644
--- a/paddle/fluid/operators/sum_op.cc
+++ b/paddle/fluid/operators/sum_op.cc
@@ -81,10 +81,10 @@ class SumOp : public framework::OperatorWithKernel {
 
     if (x_vars[0]->IsType<framework::LoDTensor>()) {
       int dtype = -1;
-      auto x_var_names = ctx.Inputs("X");
-      for (auto& x_var_n : x_var_names) {
+      for (auto& x_var : x_vars) {
         // FIXME(zcd): The input x_var may be SelectedRows or LoDTensor.
-        auto tensor = ctx.Input<Tensor>(x_var_n);
+        auto tensor = framework::GetTensorFromVar(
+            const_cast<framework::Variable*>(x_var));
         if (tensor->numel() == 0) {
           continue;
         }