diff --git a/python/paddle/fluid/io.py b/python/paddle/fluid/io.py
index b3ed094c892c6fce7184d6d98f50ed7d6d1642a3..5c4ec99c533829240ac0bcc9647acb870f3412f8 100644
--- a/python/paddle/fluid/io.py
+++ b/python/paddle/fluid/io.py
@@ -406,6 +406,9 @@ def load_vars(executor,
                 attrs={'file_path': os.path.join(dirname, filename)})
         executor.run(load_prog)
 
+        if main_program is None:
+            main_program = default_main_program()
+
         # load slice vars on pserver, if have it.
         _load_slice_up_vars(executor, dirname,
                             main_program._slice_vars_and_attrs)