Objective：To investigate the effects of exogenous hydrogen sulfide on the expression of type Ⅲ collagen，tissue inhibitor of metallo proteinase-1（TIMP-1），matrix metalloproteinase-13（MMP-13） and MMP-14 protein and myocardial fibrosis. Methods：To－tally 52 male SD rats were randomly divided into four groups（n=13）：control group，diabetes rats group（STZ group），diabetes rats treated with H2S group（STZ+H2S group），normal rats treated with H2S group（H2S group）. Diabetic rats were induced by intraperi－toneal injection of streptozotocin（STZ，40 mg/kg）. Rats in control group were only given intraperitoneal injection with equal amount of normal saline（NS）. STZ group and H2S group were injected with NaHS（the provider of H2S，100 μmol/kg） solution. The patho－logical morphological changes in myocardial fiber were analyzed by HE staining and VG staining；the expressions of type Ⅲ collagen，TIMP-1，MMP-13 and MMP-14 were analyzed by Western blot. Results：The number of rats in each group after successful modeling was 12，9，9 and 10，respectively. Compared with those of control group，collagen deposition and myocardial fibrosis increased obvious－ly，the expressions of type Ⅲ collagen，MMP-13，MMP-14 and TIMP-1 were significantly increased（P<0.01） in STZ group，which were dramatically reversed by H2S treatment（P<0.01）. Conclusion：H2S could reduce myocardial fibrosis in diabetic rats，which may be related to the inhibition of MMP-13，MMP-14 and TIMP-1 expression.