Objective: This study aims to analyze the significance of MRI in the preoperative local staging of rectal cancer by high-resolution MRI Imaging and double-contrast MRI combined with diffusion-weighted imaging(DWI) imaging technique. Methods: A total of 250 patients clinically diagnosed with rectal cancer were enrolled into this study from January 2013 to January 2016.MRI-TN preoperative staging was used for rectal cancer lesions, based on all sequences. The mesorectal fascia and circumferential resection margin involvement was evaluated and comparatively analyzed through the pathological results of the operation. Results: The overall diagnostic accuracy of T staging was 88.8%(250/222). Diagnosis accuracy rate, specificity, sensibility, PPV and NPV of rectal carcinoma T-stage by MRI were consistent with postoperative pathological T staging(kappa = 0.712, P
= 0.000). The overall diagnostic accuracy of N-stage was 75.6%(250/189). Diagnosis accuracy rate, specificity, sensibility, PPV and NPV of rectal cancer N staging by MRI were moderately consistent with postoperative pathological N-stage(kappa = 0.623, P
= 0.000). The overall diagnostic accuracy of CRM involvement was 97.6%(58/52). In judging CRM involvement by MRI, accuracy rate was 97.6%, sensibility was 100%, specificity was 97.0%, PPV was 89.7%, and NPV was 100%. Conclusion:(1) high-resolution of thin-section MRI and double-contrast MRI combined with DWI can provide the accurate T staging of preoperative rectal cancer and provide a relatively accurate multi-parameter and multi-angle N staging.(2) MRI can accurately predict CRM involvement.(3) The sagittal view can accurately measure the distance from the lesion edges to the anus, which offer visual information for preoperatively deciding whether to keep the anus or not.