Abstract: Objective To investigate the regulatory effect of endogenous hydrogen sulfide（H2S）on expression of elastin in rats with pulmonary vascular structural remodeling induced by high pulmonary blood flow. Methods Thirty-two male SD rats were randomly divided into four groups (8 rats in each group)：shunt group , shunt+PPG (propargylglycine) group , sham group and sham+PPG group . Each rat in shunt and shunt+PPG groups was subjected to an aorta-caval shunting operation to produce rat model of high pulmonary blood flow. The rats in the shunt+PPG and sham+PPG groups were intraperitoneally injected with PPG. After 4 weeks, the mean pulmonary arterial pressure (mPAP) was measured. The percentage of muscularized arteries of small pulmonary arteries of four group rats was measured by using a microscope. The expression of a-smooth -muscle actin, elastin, TGF-b, and CTGF in pulmonary artery smooth muscle cells was observed by immunohistochemistry method. Results The mPAP of the shunt+PPG group was significantly higher than that of the shunt group and sham group (P all<0.05). The percentage of muscularized arteries and partly muscularized arteries of small pulmonary arteries was increased in rats of shunt group compared to sham group (P all<0.01). While, the percentage of non-muscularized arteries of small pulmonary arteries decreased in rats of shunt group, compared with that of sham group (P<0.01). However, when PPG was used, the percentage of muscularized arteries of small pulmonary arteries increased in rats of shunt +PPG group compared to that of shunt group (P <0.01). And the percentage of non-muscularized arteries of small pulmonary arteries decreased in rats of shunt+PPG group compared with that of shunt group (P<0.01). The expression of a-smooth-muscle actin, elastin, TGF-β and CTGF of median and small pulmonary artery smooth muscle cells in shunt group significantly increased compared to that in sham group ( P all <0.01 ). While, it further increased in rats of shunt+PPG shunt group compared with rats of shunt group (P all <0.01). Conclusion The result of this study showed that endogenous of H2S might play a modulatory role in pulmonary vascular structural remodeling through inhibiting the expression of elastin of pulmonary artery from high pulmonary blood flow in rats.