Abstract: Objective:To explore the correlation between MR diffusion weighted imaging(DWI) apparent diffusion coefficient(ADC) value and HER-2 expression in middle-aged and elderly women with breast cancer. Methods:Retrospective analysis of the diffusion characteristics and ADC values of lesion tissue in MR functional imaging of 31 female breast cancer patients who were treated in our hospital from 2018 to 2019 and confirmed by surgery. Body expression. Results:The middle-aged and elderly breast cancer tissues showed high signals on the DWI images(b=0, b=800), and the cancer tissue signals were higher on the b=800 sequence than on the b=0 sequence; the range of ADC values was approximately(0.76 ±0.10) ×10^-3/mm²; ADC value range of patients with HER-2 positive expression is approximately(0.83 ±0.10) ×10^-3/mm²; ADC value range of patients with HER-2 negative expression is approximately(0.71 ±0.10) ×10^-3/mm². Conclusion:The ADC value of patients with HER-2 positive expression is higher than that of negative expression, and the HER-2 positive expression rate is higher within the range of ADC value(0.83 ±0.10) ×10^-3/mm². It can be seen that the ADC value in MR functional imaging has important reference significance for the clinicopathological classification and postoperative treatment options of middle-aged and elderly female breast cancer patients.