Objective To explore the value of spiral CT non-enhanced scan and tri-phase enhancement scanning in the diagnosis of lung cancer. Methods A total of 79 patients with lung cancer admitted to our hospital from September 2016 to January 2018 were selected, and 79 patients' clinical data and imaging data were collected to analyze and summarize the image manifestations of spiral CT non-enhanced scan and tri-phase enhancement scanning in 79 patients with lung cancer. The diagnostic sensitivity, specificity and accuracy of non-enhanced scan and tri-phase enhancement scan of lung cancer were compared. Results The net CT enhancement value of 34 patients with adenocarcinoma was (27.12? 5.13) HU, the net CT enhancement value of 21 patients with squamous cell carcinoma was (33.15±8.22) HU, and the net CT enhancement value of 24 patients with small cell carcinoma was (22.00±7.96) HU; the net CT enhancement values of lung cancer patients with different pathological types were significantly different (F=14.39, P<0.001). The sensitivity, specificity and accuracy of tri-phase enhancement scanning in the diagnosis of lung cancer were 91.13%, 89.87% and 93.67%, respectively, significantly higher than those of CT non-enhanced scan (68.35%, 63.29% and 69.62%), and the difference had statistical significance (P<0.001). The diameter of CT non-enhanced scan lesions in 79 patients with lung cancer was 1.02~5.62cm. In 41 patients, the lesions showed irregular shape and "burrs" around the lesions. In 12 patients, there were "lobulation signs" around the lesion, swelling of mediastinal lymph nodes, and a few patients with atelectasis and obstructive pneumonia. In phase iii enhanced scanning, 42 patients showed moderate enhancement, 24 patients showed slight enhancement, and 13 patients showed significant enhancement. Only 9 patients showed pleural depression. Conclusion The sensitivity, specificity and accuracy of spiral CT tri-phase enhancement scanning in the diagnosis of lung cancer are high, which can provide reliable imaging data for the clinical development of surgery programs.