diff --git a/tests/pytest/functions/function_stddev_td2555.py b/tests/pytest/functions/function_stddev_td2555.py
new file mode 100644
index 0000000000000000000000000000000000000000..a4da7d5e29b53ac9051dc39aa8af0708197dacd2
--- /dev/null
+++ b/tests/pytest/functions/function_stddev_td2555.py
@@ -0,0 +1,91 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+import taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+import numpy as np
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+
+        self.rowNum = 100
+        self.ts = 1537146000000
+        self.clist1 = []
+        self.clist2 = []
+        self.clist3 = []
+        self.clist4 = []
+        self.clist5 = []
+        self.clist6 = []
+    
+    def getData(self):
+        for i in range(tdSql.queryRows):
+            for j in range(6):
+                exec('self.clist{}.append(tdSql.queryResult[i][j+1])'.format(j+1))
+        
+    def run(self):
+        tdSql.prepare()
+
+        tdSql.execute('''create table test(ts timestamp, col1 tinyint, col2 smallint, col3 int, col4 bigint, col5 float, col6 double, 
+                    col7 bool, col8 binary(20), col9 nchar(20)) tags(cid int,gbid binary(20),loc nchar(20))''')
+        tdSql.execute("create table test1 using test tags(1,'beijing','北京')")
+        tdSql.execute("create table test2 using test tags(2,'shanghai','深圳')")
+        tdSql.execute("create table test3 using test tags(2,'shenzhen','深圳')")
+        tdSql.execute("create table test4 using test tags(1,'shanghai','上海')")
+        for j in range(4):
+            for i in range(self.rowNum):
+                tdSql.execute("insert into test%d values(now-%dh, %d, %d, %d, %d, %f, %f, %d, 'taosdata%d', '涛思数据%d')" 
+                            % (j+1,i, i + 1, i + 1, i + 1, i + 1, i + i * 0.1, i * 1.5, i % 2, i + 1, i + 1))                      
+
+        # stddev verifacation 
+        tdSql.error("select stddev(ts) from test")
+        tdSql.error("select stddev(col7) from test")
+        tdSql.error("select stddev(col8) from test")
+        tdSql.error("select stddev(col9) from test")
+
+        con_list = [
+            ' where cid = 1 and ts >=now - 1d and ts <now',
+            " where gbid = 'beijing' and ts >=now - 1d and ts <now",                       
+            ' '
+        ]
+        for condition in con_list:
+            tdSql.query("select * from test %s"%(condition))
+            self.getData()
+            for i in range(6):
+                exec('tdSql.query("select stddev(col{}) from test {}")'.format(i+1,condition))
+                exec('tdSql.checkData(0, 0, np.std(self.clist{}))'.format(i+1))
+                exec('self.clist{}.clear()'.format(i+1))
+        print('step 2')
+        con_group_list = {
+            ' cid = 2 and ts >=now - 1d and ts <now group by tbname':2,
+             " loc = '深圳' and ts >=now - 1d and ts <now group by tbname " :2 ,
+             " gbid = 'shanghai' and ts >=now - 1d and ts <now group by cid " :2
+        }
+        result = [6.922186552,6.922186552,6.922186552,6.922186552,7.614405212,10.383279829]
+        for key,value in con_group_list.items():
+            for i in range(6):
+                    exec('tdSql.query("select stddev(col{}) from test where {}")'.format(i+1,key))
+                    for j in range(value):
+                        tdSql.checkData(j, 0, result[i])
+                      
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())