Objective To investigate the clinical value of CT plain scan and enhanced scan in preoperative and postoperative evaluation of colorectal cancer resection. Methods From March 2014 to April 2015 in our hospital, 75 cases of colorectal cancer diagnosed by colonoscopy and pathological biopsy, all patients underwent CT plain scan and enhanced scan before operation. The original cross sectional images were combined and compared with surgical pathology. CT plain scan and contrast enhanced scan were used to analyze the display of the surrounding structures of colorectal cancer, and the sensitivity, specificity and accuracy of T and N staging of rectal cancer were calculated. Results The accuracy rate of CT examination in 75 cases was 100%.75 patients with pathological results as reference, spiral CT scan showed that the T stage diagnostic coincidence rate was 65.33%, the sensitivity was 76.28%, specificity was 64.39%, the diagnostic accuracy was 71.50%, the positive predictive value was 79.83%, the negative predictive value was 62.24%. The diagnostic accuracy of N staging was 62.67%, the sensitivity was 72.35%, the specificity was 67.76%, the diagnostic accuracy was 62.23%, the positive predictive value was 65.71%, and the negative predictive value was 64.55%. Preoperative CT scan shows colon tube wall thickening. CT preoperative enhanced arterial phase of intestinal wall enhanced moderately, venous phase and delayed phase enhancement of intestinal wall wall decreased, and slight enhancement; after CT scan can be seen in the colon metal suture shadow, anastomotic wall thickening was not obvious. Conclusion CT scan and enhanced scan for colorectal cancer preoperative TNM staging is more accurate, and can display the suture after operation, resection of preoperative and postoperative assessment has high clinical value in colorectal cancer.