Malignant tumors of the biliary system include extrahepatic cholangiocarcinoma, gallbladder cancer, cystic adenocarcinoma of the bile ducts, mucinous cholangiocarcinoma, carcinosarcoma of the gallbladder, and intramural papilloma of the bile ducts. These tumors are mostly found in middle-aged and old-aged people, the incidence rate of men is slightly higher than that of women, and they are closely related to biliary stones, chronic cholecystitis, and biliary parasitic infections. Imaging examination is an important means to diagnose malignant tumors of the biliary system. CT, MRI, ultrasound, and MRCP can clearly show the size, morphology, borders, bile duct dilatation, and the relationship with the surrounding tissues of the tumor. In terms of imaging, extrahepatic cholangiocarcinoma is mostly characterized by thickening of bile duct wall, narrowing of lumen, and dilatation of bile ducts; gallbladder cancer may be characterized by thickening of gallbladder wall, intraluminal mass, or disappearance of gallbladder lumen; cystic adenocarcinoma of the bile ducts and mucinous cholangiocarcinoma are often accompanied by dilatation of the bile ducts and cystic mass; and intramural papilloma is characterized by intramural papillary or polypoidal mass in the bile ducts. The imaging features of these tumors are helpful for differential diagnosis with other biliary tract diseases (e.g., bile duct stones, gallbladder polyps, cholangitis, etc.).