Objective To investigate the application value of multimodal magnetic resonance imaging (MRI), which contains high resolution and double b value diffusionweighted magnetic resonance imaging (DWI), combined with colonoscopy in the field of diagnosis and preoperative staging of rectal cancer.Methods Retrospective analysis was conducted with the MRI and colonoscopy data of 43 selected cases of patients with rectal cancer confirmed by operation and pathology from September 2017 to December 2019 in the First People’s Hospital of Guangyuan. The T staging, N staging, MRF status, EMVI status and distance from the lower edge of the tumor to anal margin of each rectal cancer patient were assessed from MRI images. Finally, the “DISTANCE” evaluation report was obtained. The comparison between the T and N staging results from MRI “DISTANCE” report and postoperative pathology was performed to understand the accuracy of MRI diagnosis.Results38 patients were assessed correctly on T staging by MRI and the overall diagnostic accuracy reached to 88.37%. The accuracy, sensitivity and specificity of MRI on T1 and T2 stages are 93.02%, 100%, 92.11%. Those of the T3 stage are 88.37%, 88.57%, 87.50% and the T4 stage are 95.35%, 66.67%, 97.50%, respectively. It could demonstrate the strong consistency between MRI diagnosis on preoperative T staging and pathological T staging of rectal cancer. 32 patients were assessed correctly on N staging by MRI with overall diagnostic accuracy of 74.42%. The accuracy, sensitivity and specificity demonstrated in three N stages are as following: 88.37%, 78.95%, 95.83% in N0 stage. 74.42%, 72.2%, 76.00% in N1 stage and 86.05%, 66.67%, 89.19% in N2 stage, respectively, which shown that the correlation between MRI in N staging and pathological N staging of rectal cancer remaining at a moderate level.Conclusion Multimodal MRI (high resolution + double b value DWI) has a great value on the staging diagnosis of rectal cancer patients, especially on T1-T2 staging. Besides, the accuracy of T staging is better than N staging, which is of significance for clinical diagnosis.