Objective To study the value of magnetic resonance （MR） T2 weighted imaging （T2WI） combined with diffusion weighted imaging （DWI） in preoperative staging of rectal cancer and its correlation with pathology. Methods This retrospective analysis was conducted on 208 patients of rectal cancer with complete imaging and pathological data from June 2020 to June 2023. All patients underwent preoperative rectal standard protocol of MRI examination, with plain and enhanced scans indicating the location and size of the tumor and DWI signals measuring the apparent diffusion coefficient （ADC） value of the tumor. We compared the diagnostic efficacy of T2WI alone and the combination of T2WI and DWI, obtained the average and minimum ADC values of tumor tissues with different pathological grades, and analyzed the correlation between the two values and pathological grades. Results The diagnostic accuracy of combined T2WI and DWI for T2 and T3 stages of rectal cancer was significantly higher than that of T2WI alone （P<0.05）. The average and minimum ADC values of low differentiated rectal cancer were significantly lower than those of medium and high differentiated rectal cancers （P<0.05）, and the minimum ADC value was negatively correlated with pathological grade（r=–0.422, P<0.05）. Conclusions The combination of T2WI and DWI has a higher diagnostic efficiency for rectal cancer than T2WI alone. In addition, the minimum ADC value has a good value for preoperative pathological grading of tumors.