Objective To investigate the diagnostic value of multi-slice spiral CT scan (MSCT) and MRI in differentiating preoperative T and N stages of colorectal cancer. Methods Sixty patients with colorectal cancer who were treated in the hospital from February 2016 to October 2017 were selected. All patients underwent MSCT and MRI scans at 1 week before surgery. With postoperative pathological stages results as the golden standard, the diagnostic value of MSCT and MRI in differentiating preoperative T and N stages of colorectal cancer was evaluated. Results With postoperative pathological stages results as the golden standard, the coincidence rates of preoperative T and N stages diagnosed by MRI in patients with colorectal cancer were significantly higher than those by MSCT (P<0.05). The image analysis results of typical cases showed that both MSCT and MRI were of application value in the preoperative stages of colorectal cancer. Conclusion The coincidence rates of MRI in the diagnosis of preoperative T and N stages of colorectal cancer are significantly higher than those of MSCT. The former is of greater application value in the diagnosis of preoperative T and N stages of colorectal cancer.