Abstract: Objective To study the regulatory effect of hydrogen sulfide (H2S) on the accumulation of collagen in thoracic aorta of spontaneous hypertensive rats (SHR). Methods Seventeen male SHR rats were randomly divided into SHR group (n=6), SHR+H2S group (n=6), SHR+PPG group (n=5). Five WKY rats were included as WKY group (n=5). NaHS, which is H2S donator, was injected peritoneally innto rats of SHR+H2S group with a dosage of 56mmol/kg everyday for 5 weeks. For rats in SHR+PPG group, D, L-propargylglycine (PPG), which is CSE inhibitor, was injected peritoneally with a dosage of 37.5mg/kg for 5 weeks. The other two groups of rats were injected with the same volume of sterile water. At the age of 9 weeks, the arterial blood pressure was measured by tail capacity method. Using the thoracic aorta as study object, the enzymatic activity of cystathionine g-lyase (CSE) was determined by enzyme facilitating reaction; the hydroxyproline quantification was measured by hyperthermia splitting method; the amount of collagen type Ⅰ was determined by ELISA method; the expression of transforming growth factor b3 (TGF-b3) was detected by immunohistochemistry method. Results For rats in SHR group, the blood pressure increased by 52%; the CSE activity decreased by 55% (p<0.01); the content of hydroxyproline increased by 87% (p<0.01); the amount of collagen type Ⅰ increased by 28%; the expression of TGF-b3 in the aortic tissue of SHR group increased by 10% (p<0.05) compared with rats in WKY group. Supplying with exogenous H2S significantly alleviate the changes of these parameters above. Conclusion Supplying exogenous H2S to SHR rats could decrease the blood pressure and reduce the content of hydroxyproline and collagen type I in the vessels, therefore, lessen the accumulation of collagen in the thoracic aorta of SHR.