Objective To investigate the role of endogenous Hydrogen Sulfide ( H2S) in airway inflammation and responsiveness in a rat model of chronic passive-smoking. Methods Male SD rats were randomly divided into a control group ( breathing fresh air) and a passive smoking group [ cigarette smoking( CS) passively] , with 18 rats in each group. Six rats in each group were randomly intraperitoneally injected with normal saline, sodium hydrosulfide ( NaHS) or propargylglycine ( PPG, an irreversible inhibitor of cystathionine- γ-lyase) . The animals were divided into six subgroups, ie. Con group, NaHS group, and PPG group, CS group, CS+ NaHS group, and CS + PPG group. After 4 months, lung histological change and airway tension were measured. The H2S levels of plasma and lung tissue were analyzed by the sensitive sulphur electrode assay. The expression of cystathionine-γ-lyase ( CSE) was measured by western blot. Results Compared with the Con group, CSE protein expression in lung tissues was increased in CS group( P lt;0. 05) ; the H2 S levels of plasma were significantly higher in CS group, NaHS group and CS + NaHS group, and much lower in PPG group ( P lt; 0. 05, respectively) . Compared with CS group, the H2S levels of plasma were significantly higher in CS + NaHS group, and much lower in CS + PPG group( P lt; 0. 05, respectively) . The H2S level of lung tissue in each group had no significant difference ( P gt; 0. 05) . Compared with Con group,score of lung pathology was significant elevated, and the responsiveness of airway smooth muscles to ACh and KCl was significant augmented in CS group. Compared with CS group, the score of lung pathology was decreased, and the responsiveness of airway smooth muscles was decreased in CS +NaHS group( P lt;0. 05) , and vise versa in CS + PPG group( P lt; 0. 01) . Conclusion H2S can alleviate airway inflammation and hyperresponsiveness induced by CS, and administration of H2S might be of clinical benefit in airwayinflammation and airway responsiveness.