Abstract: Breast cancer is one of the most ordinary malignant tumors in woman, and its mortality is only less than that of lung cancer.Early diagnosis is a key to reducing the mortality rate.The commonly used methods to diagnose breast cancer include mammography, ultrasonography, magnetic resonance imaging.Genetic changes of breast cancer comprise increased tumor blood flow, increased levels of glucose metabolism, amino acid transport, protein synthesis receptor expression, enhanced DNA synthesis and cell proliferation, and induction of apoptosis.It shows high ¹⁸F-fluorodeoxyglucose(¹⁸F-FDG) or methionine uptake in breast cancer, ¹¹C-methionine (¹¹C-MET) has a lower price.PET with ¹¹C-MET has a high prognostic value in breast cancer.