diff --git a/paddle/fluid/framework/ngraph_operator.cc b/paddle/fluid/framework/ngraph_operator.cc
index 8878917da1683606b3e5602e4981c10b88a7d735..99c4cf0da607cdb5d3282696fc7290187a3f4ed9 100644
--- a/paddle/fluid/framework/ngraph_operator.cc
+++ b/paddle/fluid/framework/ngraph_operator.cc
@@ -57,6 +57,7 @@ typedef enum {                /* nGraph support state on ops          */
                PARTIAL_TEST   /* Support partial list of ops for test */
 } op_state;
 
+// perform graph build through bridge and execute computation
 class NgraphOperator {
  public:
   explicit NgraphOperator(const Scope& scope, const platform::Place& place,
@@ -100,33 +101,33 @@ class NgraphOperator {
   std::unordered_set<std::string> post_op_inputs_;
   op_state ng_op_state_;
 
+  // ngraph backend eg. CPU
   static std::shared_ptr<ngraph::runtime::Backend> backend_;
-
+  // ngraph function to call and execute
   std::shared_ptr<ngraph::Function> ngraph_function_;
   // var_name of inputs
   std::vector<std::string> var_in_;
   // var_name of outputs from  fetch in order
   std::vector<std::string> var_out_;
-
+  // map input vars to nodes
   std::shared_ptr<
       std::unordered_map<std::string, std::shared_ptr<ngraph::Node>>>
       var_in_node_map_;
-
   // map each var name with a ngraph node
   std::shared_ptr<
       std::unordered_map<std::string, std::shared_ptr<ngraph::Node>>>
       var_node_map_;
-
+  // cache key to check if function is cached
   std::shared_ptr<std::string> GetCacheKey();
-
+  // get ngraph input and define ngraph input parameters
   void GetNgInputShape(std::shared_ptr<OperatorBase> op);
-
+  // Call ngraph bridge to map ops
   void BuildNgNode();
-
+  // get the ngraph input and output var list
   void BuildNgIO();
-
+  // build ngraph function call
   void BuildNgFunction();
-
+  // Check cache for ngraph function or otherwise build the function
   void GetNgFunction();
 };