Inclusion Criteria:  Colonoscopy diagnosed as a colorectal polyp, the number of polyps is less than 5, and the size of single polyp is less than 2.0 cm Age more than 18 years and less than 70 years  Exclusion Criteria:  Allergy to propofol, dezocine, midazolam or eggs ASA class IV, short and tick neck, difficult intubation due to inability to open the mouth widely Suspected of gastrointestinal perforation, bleeding or obstruction Acute gastrointestinal infection period History of abdominal surgery Patients during pregnancy or lactation