Breast cancer, a most common malignant tumor of women, is the leading cause of tumor deaths in women, and the incidence shows a gradually younger trend. Early screening is vital to improve prognosis of the patients. As an important functional imaging method, magnetic resonance imaging (MRI) has been widely used in the diagnosis of breast diseases. This article reviewed the application of MRI in the diagnosis, histological grade and molecular typing of breast cancer and the patient prognosis assessment, providing references for the development of MRI technology in breast cancer diagnosis.