Objectives: This study employed proteomic profiling to identify specific tumor markers that might improve early diagnosis of lung squamous cell carcinoma. Methods: Serum samples were isolated from 30 patients with stage I lung squamous cell carcinoma and 30 age-and gender-matched healthy controls, and proteomic profiles were obtained by matrix-assisted laser desorption ionization time of flight mass spectrometry. Results: Three highly expressed potential tumor markers were identified in the sera of stage I lung squamous cell carcinoma patients, with molecular weights of 3261.69, 3192.07, and 2556.92 Da. One protein peak with molecular weight 3261.69 Da was chosen as the candidate biomarker and identified as a fibrinogen alpha chain through a search of the IPI, NCBI or SWISS-PROT protein databases. Conclusion: As a potential tumor biomarker, fibrinogen alpha chain may be applicable for the early diagnosis and prognosis of lung squamous cell carcinoma patients.