Bowel preparation before colonoscopy must be performed, and it is very important that the quality of the colonoscopy, completed by the doctor, is closely related to the pre-bowel preparation. It is recommended that patients undergoing colonoscopy should strictly follow the doctor’s requirements for bowel preparation. Specifically as follows: 1, to the hospital appointment: usually 2-3 days time to make a successful appointment, a long time may also occur 1 month; 2, 3-4 days before the colonoscopy, first of all, a light diet, eat easily digestible food, do not eat too much green vegetables, indigestible food, too much meat, if the food is not well digested, the intestinal secretions will increase, affecting the observation; 3, before the colonoscopy Drink clean intestinal drugs: there are many types of drugs, according to different hospital conditions have different drug preparation, the routine includes mannitol, compound polyethylene glycol electrolyte dispersion, lactulose, magnesium sulfate, etc.. There are also more primitive herbs such as senna, etc., prepared to cleanse the intestinal tract. Routinely, the drugs that have less impact on the body are compounded polyethylene glycol electrolyte dispersions. This is because such drugs relatively keep the water in the intestine from being absorbed by the intestine for the purpose of cleansing the intestine. It is relatively safe for elderly patients and the cleaner the intestine is, the cleaner the intestine is, the better it is for the doctor to detect lesions and treat the situation microscopically.