Objective To explore the value of diffusion-weighted imaging (DWI) combined with magnetic resonance cholangiopancreatography (MRCP) in the diagnosis of ampullar obstructive jaundice. Methods A total of 62 patients with obstructive jaundice due to ampullar disease treated in the hospital from February 2015 to February 2017 were enrolled as the subjects, 30 patients were scanned by MRCP (the control group) and 32 patients were examined by MRCP and DWI (the observation group). The MRCP signs, DWI image quality and signal characteristics of all cases were analyzed and compared with the pathological examination results. Results MRCP could clearly show the structure of bile duct. The malignant diseased bile duct showed soft rattanlike dilation, and DWI showed clear masses and gallbladder wall hyperplasia. The benign lesion showed dry branch-like dilation. There was no special DWI images. The total diagnostic coincidence rates in the control group and the observation group were 63.33% and 93.75%, respectively (χ2 =6.907, P<0.05). Conclusion The diagnostic efficiency of MRCP combined with DWI for ampullar obstructive jaundice is significantly better than that of single MRCP diagnosis. It can be used as a reference scheme in clinical diagnosis.