1.Patients usually take the left side lying position with legs flexed; 2.First do rectal finger diagnosis to understand whether there is stenosis, anal fissure, hemorrhoids, etc. The operator will lubricate the end of the intestinal lens, the patient needs to breathe with an open mouth and relax the anus, the examiner holds the operating part of the colonoscope with the left hand, and the head end of the colonoscope is incorporated into the anus with the right hand; 3, after the mirror is in the anus, the action is gentle and goes straight to the ileocecal region, and when retiring the mirror, detailed observation of lesions in various parts is needed, and for valuable parts, camera, biopsy and cytological examination can be performed.