Objective To study the effects of Fufangbiejiarangan Tablets (FT) on the expression of transforming growth factor-β_1 (TGF-β_1) and mRNA in rat renal cortex. Methods To establish the rat models of renal interstitial fibrosis after unilateral ureteral obstraction(UUO). The rats were divided randomly into 7 groups: the normal group, the pseroperative group, the model group, the Benazepril group, the treatment group 1 with high dose of FT, the treatment group 2 with middle dose of FT and the treatment group 3 with low dose of FT. After the operation for four weeks the expression of TGF-β_1 and mRNA in rat renal cortex were detected respectively by immunohistochemistry and in situ hybridization. The graphic analysis system and SPSS 11.5 statistics software were used to treat the results. Results In the model group the level of TGF-β_1 and the yellow granular positive reactant of mRNA was low in the renal tubular epithellal cell and renal interstitial cell. In the Benazepril group the level of yellow granular positive reactant were obviously decreased compared with the model group (P<0.01). In the treatment groups the level of yellow granular positive reactant were obviously decreased compared with the model group (P<0.01). The treatment group 1, 2 and 3 had different dose dependency respectively. Conclusion TGF-β_1 may play an important role in renal interstitial fibrosis. FT has a protective effect on rat kidney with renal interstitial fibrosis through decreasing the levels of TGF-β_1 and mRNA.