Abstract: OBJECTIVE To investigate the effect of baicalin on A549 cells exposed to cigarette smoke extract (CSE). METHODS Cultured human lung adenocarcinoma A549 cells. Mainstream smoke was collected by using dimerhyl sulfoxide as absorbent. A549 cells were incubated with different concentrations of baicalin and CSE. Cell viability was evaluated by MTT assay. Cell apoptosis was detected by flow cytometry annexin V-FTTC/PI staining assay. Comet assay was used to detected DNA damage. The contents of reactive oxygen species (ROS) was examined by fluorescence method. RESULTS MTT assay results showed that CSE decrease the viability of A549 cells in time- and concentration-dependent manners(P<0.05). Baicalin inhibited the decrease of viability induced by CSE(P<0.05 or P<0.01), decreased the contents of ROS in A549 cells (P<0.01). The comet assay indicated that baicalin inhibited the DNA damage induced by CSE on A549 cells, tail length, tail DNA%, TM, OTM were lower than CSE group(P<0.05). And apoptosis rate of cells injured by CSE was decreased by baicalin. CONCLUSION Bacalin can inhibit the injury induced by CSE, increase viability, decrease apoptosis. The results may be related to the decrease of ROS and a lower DNA damage rate caused by baicalin.