ercp refers to transendoscopic retrograde cholangiopancreatography, after the removal of bile duct stones, bile drainage through the nasal cavity is called nasobiliary drainage, and its main role is to prevent postoperative acute cholangitis and observe postoperative bleeding. 1. Preventing postoperative acute cholangitis: nasobiliary drainage after ercp gallstone surgery can ensure smooth bile drainage and prevent the occurrence of postoperative acute cholangitis. 2. Observation of postoperative bleeding: ercp choledochotomy and lithotripsy has the risk of bile duct bleeding due to bile duct injury, and nasobiliary drainage can be observed as early as possible to see if there is bleeding after surgery and determine the site of bleeding. Nasobiliary drainage after ercp choledochotomy and lithotripsy has many benefits for patients, and the nasobiliary drainage should be closely observed after surgery. If the drainage is not smooth or there is blood in the drainage fluid, further diagnosis and treatment should be done in time to avoid delay.