Objective:To study the effect of labaplatin combined with irradiation on non-small cell lung cancer cell line A549 and explore its radiosensitizing mechanism. Methods: MTT was used to examine the effect of labaplatin and /or irradiation on lung cancer cell line A549 proliferation. Flow cytometry was applied to detect the cell cycle distribution and cell apoptosis. Western blotting was used to observe the expression of Bcl-2 and Bax. Results: Lung cancer cell line A549 could be inhibited by labaplatin in a concentration dependent manner. G2/M phase peak and apoptosis rate was the highest in cells treated with labaplatin combined with irradiation. Western blotting illustrated the decrease of Bcl-2 and the increase of Bax. Conclusion: Labaplatin could radiosensitize A549 cells and the possible mechanism might be related with inhibiting Bcl-2, inducing Bax expression and activating the Bcl-2 (Bax)-caspase signaling way.