Objective To explore the mechanisms by which hydrogen sulfide (H2S) regulates collagen metabolism during hypoxic pulmonary vascular structural remodeling. Methods Wistar rats were randomly divided into control group (n=6), hypoxia group (n = 6) and hypoxia+NaHS group(n= 6) H2S content in plasma was measured with spectrophotometry. The expression of collagen I was detected by immunohistochemistry. The expression of tissue inhibitor of metalloproteinase-1(TIMP-1) mRNA was detected with situ hybridization Results Compared with hypoxia group, H2S content in plasma increased significantly and the expressions of collagen I and TIMP-1 mRNA in pulmonary arteries were down- regulated in hypoxia + NaHS group. The H2S content in plasma negatively correlated with TIMP-I mRNA expression. Conclusions H2S increases the degradation of collagen in small and media pulmonary arteries of rats under hypoxia by decreasing the synthesis of TIMP-1, and therefore, attenuats the collagen remodeling in pulmonary arteries of hypoxic rats.