Recently, we successfully performed a case of type IV hilar bile duct cancer with vascular invasion in an elderly patient who underwent bilateral metal stenting of the right and left liver under ERCP. The patient’s total bilirubin rapidly decreased from 400µmol/l to 200µmol/l only 5 days after the operation, and he walked on the ground on the second day after the operation. The patient’s abdominal pain was relieved, his diet was gradually restored, and his quality of life was significantly improved. Type IV hilar cholangiocarcinoma usually involves all major bile duct branches in the liver parenchyma, as well as the hepatic artery and portal vein, and the rate of surgical resection is extremely low in clinical practice. Due to the deep location of the mass and obstruction of the bile duct branches, it is difficult to reveal the proximal bile ducts of the obstruction. In traditional surgery, internal drainage by bile-intestinal anastomosis is often not possible, and only an external drainage tube can be placed in one of the bile duct branches, resulting in poor post-operative yellowing reduction and frequent post-operative bile leakage, ascites and infection. Patients have to suffer from lifelong pain caused by bile loss and reduced digestive function, which significantly reduces their quality of life. ERCP surgery is a more ideal treatment for these patients. After entering the bile duct through the duodenal papilla, a series of operations such as cholangiography, intrahepatic bile duct superselective cannulation and dilation are performed, and a metal stent with morphological memory is placed at the tumor stricture to open up the bile duct obstruction so that bile can flow into the intestinal cavity and participate in digestion according to the physiological channel. While alleviating the patient’s symptoms such as jaundice and abdominal pain, the minimally invasive and fast recovery procedure has significantly improved and extended the patient’s quality of life and survival time. Since type IV hilar cholangiocarcinoma affects the bile ducts on both sides of the left and right liver, bilateral bile duct drainage is required to effectively resolve jaundice. Therefore, endoscopic bilateral metal stent drainage for hilar cholangiocarcinoma is one of the most difficult procedures in ERCP. Usually, two stents are placed into the right and left intrahepatic bile ducts at the same time and then gradually released at the same time, and only the stent with smaller sheath diameter can be placed at the same time. In this case, in order to place a large-diameter stent with the greatest support and prolong the time of stent patency after surgery, we used to place a plastic stent as a space occupancy, placed and released the first large-diameter metal stent first, and managed to place and release the second large-diameter metal stent successfully by using the space caused by the pre-placed plastic stent support more, and finally successfully pulled out the plastic stent , allowing both metal stents to be fully expanded and secured. This approach requires a very high level of skill on the part of the ERCP surgeon, but when the procedure is successful, it provides the best possible outcome for the patient.