To observe the effect of micro decoction pieces of modified Heidihuang decoction on renal fibrosis rats caused by unilateral ureteral obstruction (UUO). Methods： Rat fibrosis models were established through unilateral ureteral obstruction, then those rats were randomly divided into blank group, sham group, model control group, micro decoction pieces group, Niaoduqing group, with 10 in each group. The micro decoction pieces of modified Heidihuang decoction and Niaoduqing granules dissolved in 4ml distilled water were respectively administered intragastrically to rats in micro decoction pieces group and Niaoduqing group. Rats in the blank group, control group and model group were all gave intra-gastric administration with the same volume of distilled water. 14 days after UUO, kidney tissues of rats in each group were taken with TUNEL method to detect kidney tissue apoptosis. At the same time, Hemorheology and serum creatinine and urea nitrogen of each group rat were detected. Results： By TUNEL method, the renal tissue cell apoptosis of micro decoction pieces group and Niaoduqing group with renal interstitial fibrosis rats were improved more better than model group(P<0.01), but there was no significant difference (P>0.05).The hemorheology of Niaoduqing group improvement was better than that of micro decoction pieces group (P<0.05); the serum creatinine and urea nitrogen of micro decoction pieces group and Niaoduqing group with renal interstitial fibrosis rats were improved better than that of the model group(P<0.01 or P<0.05). Conclusion： Micro decoction pieces of modified Heidihuang decoction can relieve renal interstitial fibrosis caused by UUO in rats by improving hemorheology indexes and renal tissue cell apoptosis.