AIM:To investigate the possible preventive mechanism of Tongfu Xiezhuo Decoction(Radix astragali,Radix et Rhizoma rhei,Rhizoma acori tatarinowii,Semen pharbitidis,Radix aconiti lateralis praeparata,Radix et Rhizoma ginseng, Rhizoma atractrylodis macrocephale,Radix et Rhizoma Salviae mltiorrhizae,Semen Vaccariae,Pericarpium citri reticulate) for the tubule interstitial fibrosis by influence on the expression of ?-SMA,LN,ColⅢ in rats. METHODS: Unilateral ureteral occlusion(UUO) rats were randomly divided into 6 groups,including Sham,UUO,Enalapril group and Tongfu Xiezhuo Decoction of high-dosage,mid-dosage and low-dosage groups,the same amount of physiological saline for intragastric administration was administered by gavage.Sera and the kidney tissues were collected from each group on the twelfth day,Scr and BUN were measured.HE,VG staining measurement of tubulo-interstitial damage index and collagen deposition level,immuneohistochemical studies localizing ?-smooth muscle,actin(?-SMA),laminin-(LN),collagenⅢ(ColⅢ)were carried out. RESULTS: In UUO rats,the tubular interstitial damage index,the expressions of ?-SMA,laminin-(LN),collagenⅢ(ColⅢ) were all increased compared with those of Sham group(P