Here the investigators assume that instant messaging program (Wechat) delivery the detail and FAQ (Frequently Asked Questions) of bowel preparation instructions would improve the quality of the bowel preparation. The Wechat program has some advantages, 1. Wechat supports over 400 million users, nearly half of the mobile subscribers population in China; 2. Wechat provided a real time communications including voice messages, pictures and text exchange timely; 3.Compare with telephone, Wechat is economical of both time and money; 4. Compare with bowel preparation instructional software and litera or cartoon educational booklet, Wechat is more interactive and responsive.