The expression level of Ki-67 has an important reference value for the diagnosis, treatment and prognosis evaluation of breast cancer. To explore the feasibility of diffusion-weighted imaging for prediction of Ki-67 expression. In this study, the expression of Ki-67 in breast cancer was differentiated by semi-automatic extraction of the image parameters of diffusion-weighted(DWI) before treatment. The results of this study show that Ki-67-negative and Ki-67-positive breast cancer have different imaging characterization values in DWI images. The imaging of DWI is feasible in identifying the two, which is helpful to predict the expression level of Ki-67 in breast cancer before operation.