Abstract: Objective: To study the level of serum CEA,NSE and CYFRA21-1between lung cancer and benign lung disease,and to evaluate clinical differential diagnostic value of combined detection of serum CEA,NSE and CYFRA21-1 in patients with Lung cancer. Methods: CEA,NSE and CYFRA21-1 were assayed in 122 patients with lung cancer and 37 patients with benign lung disease. Results: The serum levels of CEA、CYFRA21-1 in patients with lung cancer were significant higher than those with benign lung disease（P＜0.05）.The sensitivity of the combined determination containing the three tumor markers were（51.64%）,being higher than other in diagnosis for lung cancer.The level of serum and the sensitivity of CEA,NSE and CYFRA21-1 were related to pathology type.The highest level of CEA,NSE and CYFRA21-1 were adenocarcinoma,small cell carcinoma and squamous carcinoma respectively. Conclusion: Serum level of CEA,NSE and CYFRA21-1 combined detection in the diagnosing of lung cancer is helpful in clinical differential diagnosis.