diff --git a/python/paddle/fluid/inferencer.py b/python/paddle/fluid/inferencer.py
index 276bc03109cfc9d9c2b764f97c0ba6615576cd2e..21277cb493881562ce3565da4bcbc0e97dafc71f 100644
--- a/python/paddle/fluid/inferencer.py
+++ b/python/paddle/fluid/inferencer.py
@@ -20,9 +20,13 @@ __all__ = [
 
 class Inferencer(object):
     def __init__(self, network_func, params, place=None):
-        self.network_func = network_func
+        # we need to generate a framework.Program by calling
+        # network_func reference: fluid.program_guard in test_word2vec.py
+        # move the default_main_program to self.program
+        # and run the default_startup program
         self.params = params
         self.place = place
 
     def infer(self, inputs):
+        # run self.program
         pass
diff --git a/python/paddle/fluid/params.py b/python/paddle/fluid/params.py
index fcdb8617a97b7ffe55b2b9682354465dc3eb5b89..8d9d8f213400d66426fee4a29d9b6644906e7ef5 100644
--- a/python/paddle/fluid/params.py
+++ b/python/paddle/fluid/params.py
@@ -27,7 +27,15 @@ class Params(object):
             self._load(path)
 
     def _load(self, path):
+        # reference: load_persistables in io.py
         pass
 
     def save(self, path):
+        # reference: save_persistables in io.py
+        pass
+
+    def add_params(self, scope):
+        # take the keys from the scope,
+        # if not already exists in self.scope,
+        # add the key and value into self.scope.
         pass
diff --git a/python/paddle/fluid/trainer.py b/python/paddle/fluid/trainer.py
index a878ed9d780509a4fbc261c39a45d99ecba8edaf..7d4c2837c101cf3c673cc9490657eedcde3be64f 100644
--- a/python/paddle/fluid/trainer.py
+++ b/python/paddle/fluid/trainer.py
@@ -34,10 +34,15 @@ class Event(Enum):
 
 class Trainer(object):
     def __init__(self, network_func, optimizer, params=None, place=None):
+        # we need to generate a framework.Program by calling
+        # network_func reference: fluid.program_guard in test_word2vec.py
+        # move the default_main_program to self.program
+        # and run the default_startup program on an empty
         self.network_func = network_func
         self.optimizer = optimizer
         self.params = params
         self.place = place
+        # TODO(helin): support distributed training
 
     def train(self, reader, num_epochs, event_handler):
         pass