Objective To study the diagnostic value of spiral CT postprocessing techniques in staging of lung cancer. Methods 120 cases of patients with lung cancer confirmed by pathology in our hospital between January 2013 and December 2015 were selected as the study objects. Before operation, routine cross-sectional CT scan and enhanced scan were performed and postprocessing techniques (multiplanar reconstruction, volume rendering, maximum intensity projection, etc.) were applied. The results of pathological staging were taken as control to compare the diagnostic coincidence rates of CT cross section and postprocessing techniques in TNM staging of lung cancer. Results T staging: The diagnostic coincidence rate of MSCT postprocessing image T2 was 92.1% of T3 was 87.5% and of T4 was 86.9% which were significantly higher than those of cross-sectional images (60.5%, 59.4%, 60.9%) (P<0.05). N staging: The coincidence rates of MSCT postprocessing images in diagnosis of N1 and N2 (90.5%, 90.6%) were significantly higher than those of cross-sectional images (66.7%, 62.5%) (P<0.05). MSCT postprocessing techniques can correctly display distant organ metastasis. TNM staging: The coincidence rates of MSCT postprocessing images in diagnosis of II phase, III phase and IV phase (90.6%, 89.5%, 100.0%) were significantly higher than those of cross-sectional images (65.6%, 63.2%, 0.0%) (P<0.05). Conclusion The accuracy of MSCT postprocessing techniques in the diagnosis of TNM staging of lung cancer is high. Before operation, MSCT postprocessing technique can be used to accurately determine TNM staging to provide basis for clinical treatment.