Alcohol should not be consumed the night before a colonoscopy as it interferes with the administration of pre-colonoscopy medications and can have an effect on the intestinal mucosa. Bowel preparation is done before colonoscopy and the bowel needs to be emptied so that lesions can be visualized. Therefore, 3 days before the colonoscopy should eat a light diet, consume some easily digestible liquid food, fast for 8 hours before the colonoscopy, and take bowel cleansing and laxative drugs on time. As alcohol will affect the use of drugs, and alcohol on the gastrointestinal tract stimulation, causing intestinal peristalsis enhancement, can lead to intestinal spot bleeding or erosion edema and other manifestations, which in turn affects the normal intestinal observation, resulting in inaccurate results of colonoscopy. It is recommended that patients follow the doctor’s instructions to prepare for colonoscopy, which is conducive to the discovery of the disease and active treatment, in order to reduce the adverse effects of the disease.