Objective To study the possible mechanism of Yishen Tongluo Fang（ 益肾通络方） in treating renal fibrosis. Methods Built rat models with renal fibrosis by subcutaneous and caudal vein injecting cationic bovine serum albumin. Fifty successful models were randomly divided into model group

control group and the low

medium and high dose groups of Yishen Tongluo Fang group

10 rats in each group

and the same batch of 10 normal rats were picked out into normal group. The low

medium and high dose groups of Yishen Tongluo Fang group were respectively given Yishen Tongluo Fang 4. 58

9. 16 and 18. 32 g /（ kg·d） to gavage. The control group was given Shenyan Siwei Pian（ 肾炎四味片） 1. 58 g /（ kg·d） to gavage and the model group and the normal group were given distilled water（ 1 ml/100 g） with the same capacity to gavage

once a day for four weeks. Measure the transforming growth factor-β1（ TGF-β1）

average grey value of Smad7

average optical density value

number of positive cells and positive rate in the renal tissue of rats using immunohistochemical method combining with system of image analysis and made correlation analysis. Results The expression of TGF-β1 of the renal tissue in the model group under optical microscope was obviously increased

but Smad7 was unobviously expressed. Compared with the model group

TGF-β 1 average grey value

positive rate and the number of positive cells of renal tissue decreased significantly in each dose group of Yishen Tongluo Fang and the control group. The average grey value of Smad7

positive rate and the number of positive cells obviously increased and effects were more remarkable in medium and high dose of Yishen Tongluo Fang group（ P < 0. 05 or P < 0. 01）. The correlation analysis showed that the correlation between TGF-β 1 and Smad7 was linear negative（ P < 0. 01）. Conclusion The mechanisms of Yishen Tongluo Fang treating renal fibrosis may adjust the interaction relations between TGF-β 1 and Smad7

promote the expression of Smad7 and inhibit the expression of TGF-β1.