Colonoscopy is a test that is performed by inserting a colonoscope through the anus and into the ileocecal region, mainly to observe colon lesions. Colonoscopy can be considered if the patient finds bleeding in the stool, increased frequency of stool, irregularity, or abdominal pain. Before colonoscopy, bowel preparation should be performed. Patients without constipation should eat food with less residue 1 day before the examination, avoid vegetables, lean meat and other high-fiber foods, and take bowel cleansing drugs to cleanse the intestines 1 night before the examination and in the early morning of the examination day as required to keep the intestines free of fecal residue, and the examination results are better. Patients with constipation have complicated preparations before the examination, eat easily digestible food with less residue and take laxatives 2-3 days before the examination, and after slight diarrhea, then prepare for bowel cleansing according to the normal colonoscopy before the examination.