diff --git a/paddle/fluid/framework/parallel_executor.cc b/paddle/fluid/framework/parallel_executor.cc
index 335a063c4b00fb5b72070d89ebcae0c14953d546..344587897fcf5d36e60e73dc7189dff8bd9aef22 100644
--- a/paddle/fluid/framework/parallel_executor.cc
+++ b/paddle/fluid/framework/parallel_executor.cc
@@ -253,7 +253,7 @@ struct FetchOpHandle : public OpHandle {
 
 class ParallelExecutorPrivate {
  public:
-  explicit ParallelExecutorPrivate(size_t num_threads = 0)
+  explicit ParallelExecutorPrivate(size_t num_threads = 12)
       : pool_(num_threads == 0 ? nullptr : new ThreadPool(num_threads)) {}
 
   std::vector<platform::Place> places_;