Objective To observe the influences of Hongbeiyegen （ Stipellaria trewioides Benth. ） on the changes of hemorheology and microcirculation in rats with renal interstitial fibrosis （ RIF） induced by unilateral ureteral obstruction （ UUO）

and to study the mechanism of Hongbeiyegen in antagonizing RIF based on the theory of collateral disease. Methods The rat model of RIF was established by applying unilateral ureteral ligature

and then the rats were randomly divided into the model group

Hongbeiyegen group and sham-operation group. The influences of Hongbeiyegen were observed on the whole blood viscosity at shear rates of 150/s

30/s

5/s and 1/s

hematocrit （ Hct） and changes of sublingual and auricle collateral vessels. Results Hongbeiyegen reduced significantly the whole blood viscosity at shear rates of 150/s

30/s

5/s and 1/s

Hct

and levels of hyaluronic acid （ HA）

laminin （ LN）

type Ⅲ procollagen （ PC Ⅲ）

type Ⅳcollagen （ CⅣ）

serum creatinine （ SCr） and blood urea nitrogen （ BUN） index

and improved the circulation of sublingual and auricle collateral vessels. Conclusion Hongbeiyegen can improve the hemorheology and microcirculation in rats with RIF

which indicates that activating blood circulation and freeing the collaterals may be one of the mechanisms of antagonizing RIF by Hongbeiyegen.