Objective:To Investigate whether total triterpene acids(TTAs),isolated from Corpus Fructus,attenuates renal function by reducing oxidative stress and down-regulating the expression of transforming growth factor β_1(TGF-β_1).Methods:Diabetes was induced by an injection of streptozotocin(40 mg/kg intravenously).Thirty rats were randomly divided into three groups:control group,diabetic model group and TTAs treatment group(50 mg/kg,intragastrically)administrated for 8 weeks from 5th to 12th week.All rats were anaesthetized and then were killed to remove kidneys.The renal function and redox enzyme system parameters were tested.Glomerular morphology was observed by a light microscopy.Immunohistochemistry and Western blot assays were employed to determine the protein levels of TGF-β_1.Results:TTAs attenuated the levels of urinary protein,serum creatinine and blood urea nitrogen,although it did not significantly reduce the level of glucose.In addition,TTAs decreased the malondialdehyde while increased superoxide dismutase,catalase and glutathione peroxide activities in diabetic rats.The renal pathological changes in TTAs treatment group were ameliorated.Furthermore,TTAs also ameliorated the expression of TGF-β_1.Conclusion:TTAs improved renal function via reducing oxidative stress and down-regulation the expression of TGF-β_1 in diabetic rats. Objective: To Investigate whether total triterpene acids (TTAs), isolated from Corpus Fructus, attenuates renal function by reducing oxidative stress and down-regulating the expression of transforming growth factor β_1 (TGF-β_1). Methods: Diabetes was induced by injection of streptozotocin (40 mg / kg intravenously) .Thirty rats were divided into three groups: control group, diabetic model group and TTAs treatment group (50 mg / kg, intragastrically) administered for 8 weeks from 5th to 12th week. All rats were anaesthetized and then were killed to remove the kidneys. The renal function and redox enzyme system parameters were tested. Glomerular morphology was observed by a light microscopy. Immunohistochemistry and Western blot assays were employed to determine the protein levels of TGF-β_1. Results: TTAs attenuated the levels of urinary protein, serum creatinine and blood urea nitrogen, although it did not significantly reduce the level of glucose. In addition, TTAs decreased the malondialdehyde whil e increased superoxide dismutase, catalase and glutathione peroxide activities in diabetic rats. The renal pathological changes in TTAs treatment group were ameliorated. Fultrthermore, TTAs also ameliorated the expression of TGF-β_1. Conflux: TTAs improved renal function via reducing oxidative stress and down- regulation the expression of TGF-β_1 in diabetic rats.