Abstract： Objective To investigate the value of nuclear magnetic resonance apparent diffusion coefficient(ADC)in the differential diagnosis of benign and malignant breast diseases. Methods Forty-two patients diagnosed with benign and malignant breast diseases by surgical pathology in the Department of Thyroid and Galactophore,Shenzhen Municipal Maternal and Child Health Hospital between December 2013 and October 2015 were retrospectively analyzed,including 10 cases of breast cancer,12 of breast cyst,9 of mastitis,and 11 of breast fibroma. All patients underwent preoperative breast MRI and DWI examinations using single shot sequence of EPI sequence with b values of 0 s/mm2 and 800 s/mm2,respectively. In the subjects received routine breast examination,the ADC values of 12 healthy normal breast areas were included as the control group,and the difference in ADC value between the two groups was compared. Results The ADC values in the breast cancer, breast cyst,mastitis,breast fibroma and normal breast areas were(1.08±0.27)×10-3 mm2/s,(2.02±0.10)×10-3 mm2/s,(1.44±0.51)×10-3 mm2/s,(1.68±0.48)×10-3 mm2/s,(2.15±0.21)×10-3 mm2/s,respectively,and there was statistically significant difference in the groups(F=49.032,P=0.000). Except for mastitis and breast cyst, there was statistically significant difference between the groups(P<0.05). Conclusion The measurement of ADC value can provide the basis for differential diagnosis of benign and malignant breast diseases.