Abstract: [Objective]To observe the improving effect of oxymatrine(OMT)on liver fibrosis in rats induced by thioacetamide(TAA)and to assess its regulative effect on the level of TGF-β1 in fibrotic liver tissue of rats.[Methods]Rats were divided into negative control group,model group,the high-,medium-and low-dose OMT groups,and silymarin positive control group.Except for the negative control group,the other groups were subjected to the intraperitoneal injection of thioacetamide(TAA)to induce a liver fibrosis.The three OMT intervention groups and the positive control group were intragastrically administered with high-,medium-and low-dose of OMT and silymarin,respectively,and the model group and negative control group were administered with normal saline.Blood samples and liver tissues were recovered from rats in different groups,and the serum contents of alanine aminotransferase(ALT),aspartate aminotransferase(AST)and glutathione(GSH)as well as the level of liver TGF-β1 were determined,respectively.[Results]Compared to the negative control group,the model group had extremely significantly higher contents of ALT(P<0.01)and AST(P<0.01)in serum and extremely significantly higher levlel of TGF-β1(P<0.01)in liver tissue,but had extremely significantly lower serum content of GSH(P<0.01);compared to the model group,the three OMT intervention groups and positive control group had significantly lower contents of ALT(P<0.05)and AST(P<0.05)in serum and significantly lower levlel of TGF-β1(P<0.05)in liver tissue,the high-and medium-dose OMT groups had extremely significantly higher serum content of GSH(P<0.01),and the low-dose OMT group had significantly higher serum content of GSH(P<0.05).[Conclusions]OMT significantly down-regulates the gene expression of TGF-β1 in fibrotic liver tissue of rats,suggesting that inhibiting the expression of TGF-β1 in liver tissue may be one of the mechanisms underlining the therapeutic effects of OMT on liver fibrosis.