Objective:To investigate the mechanism of reducing renal interstitial fibrosis of chronic pyelonephritis with Erding-erxian Decoction by adjusting estrogen.Method:Fifty SD female rats were made into castrated chronic pyelonephritis models by cutting both sides of ovaries and putting Escherichla coli to incompletely obstructed ureter from bladder.They were randomized into 5 groups

model group

norfloxacin with premarin group（0.875 g·kg-1+0.044 g·kg-1）

Erding Decoction group（25 g·kg-1）

Erxian Decoction group（35.4 g·kg-1）

Erding-erxian Decoction group（60.4 g·kg-1）.And other 10 normal SD female rats were raised in the same period of time.The rats in each group were fed different relative drugs by intragastric administration once every day for six weeks.Urine

blood and renal tissues were taken after the treatment

while the urine regular test

urinary protein

urinary β2 microglobulin β2-MG

plasma estrogen were tested and renal pathological change were observed including transforming growth factor-β（TGF-β1） and α-smooth muscle actin（α-SMA） using immunochemistry staining method.Result:Erding-erxian Decoction could greatly improve the estrogen of castrated female rats suffering from chronic pyelonephritis.The effect was better than other groups.It could be an important mechanism of reducing TGF-β1 and α-SMA of the renal tissues so as to relieve renal interstitial fibrosis.Conclusion:Erding-erxian Decoction could relieve renal interstitial fibrosis in castrated female rats suffering from chronic pyelonephritis.