The first step of colonoscopy is to cleanse the intestines, usually by starting oral administration of compound polyethylene glycol electrolyte dispersion around 4-5 o’clock in the morning of the same day, usually three boxes of oral administration, and then cleanse the stools. After cleaning the intestines, the colonoscopy is completed, and most of the colonoscopies are performed by general colonoscopy and painless colonoscopy. The patient is awake during the whole procedure of general colonoscopy, mainly in the left lateral position, and then the sigmoid colon, descending colon, transverse colon, ascending colon and various parts of the ileocecal region are observed after the anus is inserted into the colonoscope. Depending on the results of the examination, pathological examination is also required when necessary. For painless colonoscopy, propofol is given intravenously and the patient sleeps throughout the procedure without any pain or sensation.