To investigate the correlation between the ADC value of MRI-DWI and the pathological prognostic factors of rectal cancer. 87 patients with rectal cancer were grouped according to the pathological prognostic factors. The mean ADC values of tumor tissues were measured, and the relationship between ADC values of different groups was analyzed. The differences of ADC values of the different differentiation groups, pN stage groups and P53 expression groups had statistical significance. The P53 expression level and ADC value showed a moderate negative correlation. It is expected the biological behavior of tumors can be predicted by quantitative analysis of ADC values.