Objective To conclude the intraductal ultrasonography ( IDUS ) characteristics of cholangiocarcinoma and improve endoscopic diagnosis for cholangiocarcinoma by comparing manifestations of IDUS between cholangiocarcinoma and benign bile duct stricture. Methods A total of 52 patients undergoing endoscopic retrograde cholangiopancreatography ( ERCP ) and IDUS with definite diagnosis of cholangiocarcinoma from January 2012 to January 2017 were included in this retrospective study, and 59 patients undergoing ERCP and IDUS during the same period with definite diagnosis of benign bile duct stricture were included as control. Clinical data, indices of laboratory tests, and manifestations of IDUS ( including length of stricture, echo feature, thickness of bile duct, symmetry, and integrity of outer membrane of bile duct wall) were collected and compared between the two groups. Results The clinical manifestations and results of laboratory examination showed no significant differences between the two groups. Intraductal brushing cytology and forceps biopsy showed 28. 9％ and 40. 0％ malignant evidence respectively. IDUS showed thicker bile duct in the cholangiocarcinoma group (6. 8±4. 0 mm VS 4. 1±2. 3 mm, P<0. 01). Proportion of hypoechoic and nonsymmetrical thickened bile duct was higher in the cholangiocarcinoma group( 78. 8％ VS 44. 1％, 92. 3％ VS 50. 8％, respectively, all P<0. 01 ) . Outer membrane of bile duct destruction occurred in 8 cases ( 15. 4％) in the cholangiocarcinoma group, whereas none was seen in the control group. Conclusion Hypoecho and nonsymmetrical thickness on IDUS may be indicators of cholangiocarcinoma, and destruction of bile duct outer membrane is highly suggestive of cholangiocarcinoma.