OBJECTIVE: To study the inhibitory effect of flavonoids from Glycyrrhiza uralensis on thioacetamide-induced chonic hepatic fibrosis in rats and the effect on the protein expressions of transforming growth factor-ß1 (TGF-ß1) and Caspase-3 in livers. METHOD: Male Sprague-Dawley rats were randomly divided into totally seven groups: the normal control group, the model group, LF groups s (400, 200, 100, 50 mg · kg(-1) · d(-1)) and the silymarin positive control group (30 mg · kg(-1) · d(-1)). The hepatic fibrosis model was induced in the rats through intraperitoneal injection with 3% thioacetamide (TAA) at a dose of 150 mg · kg(-1) body weight twice a week for 12 weeks. During the course, the control group and the model group were orally administered with saline (1 mL · kg(-1) · d(-1)). After the modeling and drug intervention, the pathologic changes and fibrosis in liver tissues were observed by HE staining and Masson's Trichrome staining. The serum alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and liver hydroxyproline (HYP) contents were assayed by biochemical process. The serum hyaluronic acid (HA) was assessed by radioimmunoassay. In addition, the protein expressions of liver TGF-ß1 and Caspase-3 were examined by immunohistochemical method. The mRNA expression of TGF-ß1 in hepatic tissues was examined by quantitative Real-time PCR analysis. RESULT: Compared with the model group, flavonoids can protect the integrity of the structure of liver tissues, significantly reduce the hepatic cell degeneration and necrosis and the proliferation of fibrous tissues, notably reduce the serum AST, ALT, ALP and HA and HYP in hepatic tissues and down-regulate the protein expressions of liver TGF-ß1 and Caspase-3 and the mRNA expression of TGF-ß1 in hepatic tissues. CONCLUSION: The licorice flavonoids can resist the thioacetamide-induced hepatic fibrosis in rats. Its mechanism may be related to the down-regulation of the protein expressions of TGF-ß1 and Caspase-3.