Objective To explore the application value of multi-slice spiral CT in the clinical diagnosis of rectal cancer. Methods 54 cases of patients with rectal cancer who were admitted into our hospital between May 2011 and November 2015 were retrospectively analyzed. All patients were examined by Philips CT. The results of T stage, N stage and M stage were determined and compared with the postoperative pathological results. Results The main spiral CT findings of rectal cancer were localized soft tissue mass, rectum - sigmoid colon wall thickening (circular or semi-circular), exserted growth into the cavity, with homogeneous density and low-density ischemic necrosis area when tumor was large. After injection of contrast agent, CT value increased by about 30%. Based on pathological results, the diagnostic accuracy of 16 slice spiral CT in T stage, N stage and M stage were 88.9% (48/54), 66.7% (36/54) and 96.3% (52/54) respectively. Conclusion Multi-slice spiral CT has relatively higher coincidence rate in the diagnosis of rectal cancer in T stage and M stage. It can well display tumor lesions and the structure of lesions. It is a reliable examination method of rectal cancer, and is conducive to the development of clinical treatment regimen for patients.