Objective To analyze and compare the efficacy of ultrasound, MRI and their combination in the diagnosis of breast cancer. Methods Eighty patients with breast cancer who were admitted to our hospital between September 2012 and December 2016 were selected as study subjects. All patients underwent Doppler ultrasonography, MRI scan and enhanced scan. With the pathological diagnosis as the basis, the diagnostic accuracy rates of ultrasonography, MRI and ultrasound combined with MRI were compared, and the ultrasonic and MRI findings of breast cancer were analyzed. Results Among 80 cases with breast cancer, there were 53 cases with pathologically confirmed invasive ductal carcinoma, 13 cases with invasive lobular carcinoma, 5 cases with intraductal carcinoma, 5 cases with mucinous adenocarcinoma and 4 cases with medullary carcinoma. The diagnostic accuracy rate of ultrasound combined with MRI (97.50%) was significantly higher than that of ultrasound diagnosis (85.00%) and MRI (87.50%) (P＜0.05), and the diagnostic accuracy showed no statistically significant difference between ultrasound and MRI (P＞0.05). The ultrasonic findings included diameter of lesions＞1cm, irregular shape of masses, blurred edges, spiculation, low and unevenecho, grit calcification, axillary lymph node disorders, grade II-IIIblood flow signals and rich blood flow. MRI findings included boundaries of breast tissues, irregular edges, lobulated, spiculation and punctate calcification. Plain T1WI showed low signal, T2WI showed high signal or slightly high signal, and the internal signal was inhomogeneous. Enhanced scan showed inhomogeneous or separated enhancement. Conclusion Both ultrasound and MRI can better display the internal structures and characteristics of breast cancer. They have their own advantages and disadvantages, and the accuracy of combined diagnosis of breast cancer is high, with high application value.