Objective To explore the ultrasound characteristics of intraductal papillary mucinous neoplasm of the bile duct( IPM N-B) and evaluate its diagnostic value . Methods Seventeen cases of IPM N-B were diagnosed by ultrasonic examination and confirmed by surgery and pathology . The ultrasound findings and distribution of color Doppler flow signals were observed and analyzed in comparison with the surgical and pathological results . Results Ultrasound revealed the characteristics of IPMN-B:① Bile duct mural nodules that looked like papillary or polypoid were observed; ② Asymmetry bile duct dilatation ,namely obvious dilatation in the lesion intrahepatic bile duct ,but only mild dilatation in the normal intrahepatic bile duct ;③Typical lesions showed mucus in bile duct along bile duct wall without acoustic shadow or move . High frequency ultrasound revealed that mucus in bile duct could float that looked like gelatin when operator vibrated probe in those superficial lesions . This is reliable characteristics of IPMN-B by ultrasound . Conclusions Ultrasound is of high value in the diagnosis of IPMN-B .