It is best to drink all 3000ml of the laxative before the colonoscopy. The main purpose of drinking laxatives before colonoscopy is to clean the intestinal fecal debris, if the intestinal tract is not cleaned up before the colonoscopy, it may affect the results of the examination, and the examined person should preferably drink all the laxatives, so that the intestinal feces can reach the standard of intestinal cleansing. When taking laxatives should be careful, generally need to start drinking about 6 hours in advance before the colonoscopy, at the same time, pay attention to appropriate hydration, to prevent dehydration, the examinee should follow the instructions and the doctor’s instructions for medication, pay attention to the laxative should not be taken at once all the laxatives can be divided into several times to take slowly, to prevent the phenomenon of vomiting. After taking the laxative, the patient should walk around and massage the abdomen to promote defecation. If the stool is watery, it suggests that the intestinal tract is cleaned up relatively well, usually do not need to continue to take laxatives.