The investigators will recruit patients according to admission criteria and exclusion criteria.The patients stratified by malignant and benign biliary obstruction will be randomly divided into 25cm suspended overlength biliary stents group (experimental group) 、30cm suspended overlength biliary stents group (experimental group) and ordinary plastic biliary stents group (control group).The test groups will be placed the 25cm or 30cm suspended overlength biliary stents in introhepatic bile duct in ERCP. The control group will be placed ordinary plastic biliary stents in ERCP. The main result is stent occlusion rate 12 months after ERCP.