diff --git a/jieba/__init__.py b/jieba/__init__.py
index 9b696b4..b99a686 100644
--- a/jieba/__init__.py
+++ b/jieba/__init__.py
@@ -295,8 +295,10 @@ def __lcut_all(sentence):
 def __lcut_for_search(sentence):
     return list(__ref_cut_for_search(sentence))
 
+import multiprocessing
+
 @require_initialized
-def enable_parallel(processnum):
+def enable_parallel(processnum=multiprocessing.cpu_count()):
     global pool,cut,cut_for_search
     if os.name=='nt':
         raise Exception("jieba: parallel mode only supports posix system")
diff --git a/test/parallel/test_file.py b/test/parallel/test_file.py
index 8372596..e10d1a2 100644
--- a/test/parallel/test_file.py
+++ b/test/parallel/test_file.py
@@ -3,7 +3,8 @@ import sys,time
 import sys
 sys.path.append("../../")
 import jieba
-jieba.enable_parallel(4)
+
+jieba.enable_parallel()
 
 url = sys.argv[1]
 content = open(url,"rb").read()