Background: Serum tumor abnormal protein (TAP) level has been confirmed to be associated with the progress of tumor cells. Objective: This study aimed to investigate the diagnostic value of TAP in lung cancer patients. Methods: 159 patients with lung cancer and 45 patients with benign pulmonary nodules were enrolled in this study. We measured serum TAP level and explored the relationship between TAP level and disease. Results: Serum TAP level of lung cancer patients were higher than that in benign diseases (123.4±45.4µm2 versus 104.2±25.4 µm2, P=0.0073). The results showed that TAP levels were reliable in distinguishing lung cancer from benign diseases with an area under the curves (AUC) value of 0.6222 (95% CI, 0.5360-0.7083). In addition, we observed that TAP level were associated with the pathological classification of lung cancer. The AUC values for ADC, SCC and SCLC were 0.6031(95%CI, 0.5110-0.6952), 0.6656(95%CI, 0.5373-0.7939) and 0.8089(95%CI, 0.5531-1.065), respectively. Conclusion: TAP might be a valuable biomarker for the diagnosis of lung cancer.