[Abstract] Objectives: To investigate diagnostic value of ultrasound and magnetic resonance imaging (MRI) for malignant and benign breast lesions. Methods: Retrospective analysis of treatment data of 48 patients diagnosed with malignant and benign breast lesions in our hospital, collected from December 2017 to November 2018. A total number of 56 breast masses were examined by both ultrasound and MRI, and were compared with postoperative pathological biopsy results. Results: Postoperative pathological biopsy results showed that there were 26 and 30 malignant and benign lesions respectively. Comparison of MRI curve type of malignant and benign lesions showed statistical significance (P<0.05). By comparison with pathological biopsy results, specificity and sensitivity of ultrasound diagnosis were 83.33% (25/30) and 84.61% (22/26) respectively; specificity and sensitivity of MRI diagnosis were 96.66% (29/30) and 92.30% (24/26) respectively. Conclusions: Ultrasonographic examination of malignant and benign breast lesions is straight-forward, simple and inexpensive. Accuracy, specificity and sensitivity of MRI are significantly higher than ultrasound in examining malignant and benign breast lesions, this can reduce misdiagnosis.