1.Diagnostic laboratory examination of bile duct cancer: It mainly shows abnormal liver function of obstructive jaundice, such as increase of bilirubin and alkaline phosphatase, etc. 2.Diagnostic ultrasound examination of bile duct cancer: repeated and careful ultrasound examination can show dilated bile ducts, obstructed parts and even tumors. Ultrasound images of bile duct cancer can be mass-like, striated, protruding and thrombotic. Intrahepatic bile duct cancer is often mass-like or striated, hilar cancer is often striated, lower bile duct cancer is often protruding, and thrombotic image of hilar region may be hilar cancer, gallbladder cancer or metastatic cancer. Since bile duct dilatation occurs before jaundice, ultrasound has the value of diagnosing early bile duct cancer. 3.Diagnosis of bile duct cancer PTC: It is the main method to diagnose bile duct cancer, it can show the location and scope of bile duct cancer, and the confirmation rate can reach 94%~100%. 4.CT: The basic performance of cholangiocarcinoma CT is (7) to show that the proximal bile duct of cholangiocarcinoma is obviously dilated. The wall of the bile duct near the tumor is thickened, and the bile duct can be enhanced more clearly in the enhanced scan, and the lumen of the duct is unplanned narrowing and deformation. Generally, soft tissue density tumor shadow can be found, and its CT value is 50Hu, and the enhanced CT value is 60-80Hu on enhanced scan. ② Most of the tumors grow infiltratively along the bile duct wall. The bile duct wall is thickened with poorly defined margins, which can be easily revealed by enhancement scan. Few of them are polyp-like or nodular in the lumen, and the nodules are soft tissue density. (3) Tumor infiltrates and expands into the lumen, and the duct wall margin is blurred. It often invades the gallbladder and liver, adjacent blood vessels and lymphatic tissue. And it shows uneven density soft tissue shadow, irregular morphology, blurred tissue structure and unclear boundary. 5.ERCP: direct observation of the duodenal papilla is possible, and the angiography can show the distal bile duct of obstruction. 6.Angiography: Angiography can better determine whether cholangiocarcinoma can be resected. 7.Cytological examination: on the basis of PTCD, fiberoptic cholangioscope can be inserted by enlarging the sinus tract, and the mass can be directly observed and biopsied by clamping. When PTC or PTCD is performed, bile can be extracted for cytological examination.