Objective To investigate the value of ultrasound diagnosis of extrahepatic bile duct diseases and the causes of missed diagnosis. Methods A retrospective analysis of 685 cases of extrahepatic bile duct diseases diagnosed by endoscopic retrograde cholangiopancreatography (ERCP), surgery and pathology was conducted to analyze the causes of missed and misdiagnosis of extrahepatic bile duct diseases by ultrasound. Results: In 685 cases of extrahepatic bile duct diseases, the diagnostic compliance rate of ultrasound diagnosis was 89.34%. Among them, 88.64% (468/528) were extrahepatic bile duct stones, 88.16% (67/76) were extrahepatic bile duct cancer, 92.59% (50/54) were biliary ascariasis, 100% (27/27) were cystic dilatation of common bile duct, and 73 cases were missed and misdiagnosed. Conclusion Ultrasound has high diagnostic value for extrahepatic bile duct diseases.