diff --git a/pydu/cmd.py b/pydu/cmd.py
index de2f0d0..fccc147 100644
--- a/pydu/cmd.py
+++ b/pydu/cmd.py
@@ -6,7 +6,14 @@ from .platform import WINDOWS
 from .compat import PY2
 
 
-def run(cmd, wait=True, shell=True, timeout=0, timeinterval=1):
+def run(cmd, wait=True, shell=False, timeout=0, timeinterval=1):
+    """
+    Run cmd.
+    If `wait` is True, run cmd util finish. Default to be True.
+    If `shell` is True, run cmd in shell. Default to be False.
+    if `timeout` is bigger than 0, run cmd with timeout. Default to be 0, means not timeout.
+    `timeinterval` comes with `timeout`, it means process status checking interval.
+    """
     p = Popen(cmd, shell=shell, stdout=PIPE, stderr=STDOUT)
     if not wait:
         return p
@@ -23,7 +30,7 @@ def run(cmd, wait=True, shell=True, timeout=0, timeinterval=1):
     return p.poll(), stdout
 
 
-def run_with_en_env(cmd, wait=True, shell=True, timeout=0, timeinterval=1):
+def run_with_en_env(cmd, wait=True, shell=False, timeout=0, timeinterval=1):
     """
     Run cmd with English character sets environment, so that the output will
     be in English.
diff --git a/tests/test_cmd.py b/tests/test_cmd.py
index 73c4150..14086d1 100644
--- a/tests/test_cmd.py
+++ b/tests/test_cmd.py
@@ -7,25 +7,25 @@ from pydu.cmd import run, run_with_en_env, cmdline_argv
 
 
 def test_run():
-    retcode, output = run('echo hello')
+    retcode, output = run('echo hello', shell=True)
     assert retcode == 0
     assert safeunicode(output).rstrip('\r\n') == 'hello'
 
-    p = run('echo hello', wait=False)
+    p = run('echo hello', wait=False, shell=True)
     assert p.wait() == 0
 
     retcode, output = run('{} -c "import time; time.sleep(1)"'.format(sys.executable),
-                          timeout=0.2, timeinterval=0.05)
+                          shell=True, timeout=0.2, timeinterval=0.05)
     assert retcode != 0
     assert 'timeout' in output
 
 
 def test_run_with_en_env():
-    _, output = run_with_en_env('nocmd')
-    assert output.decode('ascii')
+    _, output = run_with_en_env('nocmd', shell=True)
+    output.decode('ascii')
 
-    _, output = run_with_en_env(['nocmd'])
-    assert output.decode('ascii')
+    _, output = run_with_en_env(['nocmd'], shell=True)
+    output.decode('ascii')
 
 
 def test_cmdline_argv():