The commonly used laxative for colonoscopy is polyethylene glycol, usually 1 packet of electrolyte powder should be taken with at least 1000ml of water, which is the minimum amount. Of course in the clinical examination before the colonoscopy drink electrolyte powder at least 2 packets of divided doses, usually 1 day before the examination to drink 1 packet, the day of the examination, according to the time in advance at least 6 hours or more to drink another 1 packet or 2 packets, each 1 packet of at least 1,000 ml of water to be taken. Of course, if you don’t restrict drinking water under the permitted conditions, more drinking water plus exercise after drinking water can effectively ensure the cleanliness of defecation, which can ensure the cleanliness of the clinic when doing colonoscopy, avoiding the uncleanness of the intestinal lumen due to too much stool or mucus, which affects the results of colonoscopy.