Exclusion criteria:(1)patients taking antiplatelet or anticoagulant therapy during the past 1 week of the procedure;(2) known coagulopathy;(3) history of inflammatory bowel diseases;(4)polyposis syndrom;(5)Type IV shantian colorectal polyps;(6)American Society of Anesthesiology class III or more;(7) pregnancy;(8)Unable to provide informed consent.