Objective: To explore the effects of hydrogen sulfide (H 2S) on hypoxic pulmonary vascular smooth muscle cell (VSMC) apoptosis in rats. Methods: Twenty four Wistar rats were divided into 3 groups: control group ( n =8), hypoxia group ( n =8), and hypoxia +NaHS group ( n =8). The plasma level of H 2S was determined by methylene blue spectrophotometric method. VSMC apoptosis was measured by terminal deoxynucleotidyl transferase biotin nick end labeling (TUNEL). The protein expressions of Bcl 2, Fas and caspase 3 in pulmonary arteries were detected by immunohistochemical technique. Results: Compared with rats in the control group, the plasma level of H 2S decreased by 36% in rats of hypoxic group . The apoptotic rate per area in VSMCs detected with TUNEL was significantly decreased by 52.9% in rats of hypoxic group . The expressing integral score of Bcl 2 of VSMCs was increased by 123.9%,while Fas protein expression of VSMCs was decreased by 45% and caspase 3 protein expression of VSMCs was not significantly changed in rats of hypoxia group. But compared with rats in the hypoxia group, the plasma level of H 2S increased by 65% in rats of hypoxia+NaHS group. The apoptotic rate in VSMCs of TUNEL was significantly increased by 62.5% in rats of hypoxia+NaHS group. The Bcl 2 protein expression of VSMCs was decreased by 36.4% in rats of hypoxia+NaHS group. The expressing integral scores of Fas and caspase 3 were significantly higher in rats of hypoxia+NaHS group than in those of hypoxia group. Conclusion: Hypoxia decreased the pulmonary artery smooth muscle cell apoptosis. H 2S inhibited Bcl 2 protein expression of VSMCs and activated Fas and caspase-3 protein expressions of VSMCs, and therefore promoted the pulmonary artery smooth muscle cell apoptosis.