Objective To observe the effects and possible mechanism of kidney-warming spleen-fortifying formula on diabetic nephropathy（DN） rats.Methods Thirty six DN rats induced by Streptozotocin（STZ） were randomized into model control group

kidney-warming spleen-fortifying group and valsartan group

with 12 in each.The rats were given 10ml/kg distilled water

20g/kg kidney-warming spleen-fortifying formula and 25mg/kg valsartan for 8 weeks respectively.Twelve normal rats were chosen as the normal control group（10ml/kg distilled water）.The body weight

renal function

serum protein level

renal cortex blood flow and hemorheology indexes were detected after 8weeks.Results Comparing with the normal control group

the body weights of DN rats were decreased

the levels of glucose（GLU）and blood urea nitrogen （BUN）were increased and the levels of total protein（TP）and albumin（ALB） were decreased in the model control group（P<0.01）.Comparing with the model control group

the levels of BUN were significantly decreased and the levels of TP were significantly increased in all administration groups（P<0.05or P<0.01）.Comparing with the normal control group

the renal cortex micro-circulation blood flow was significantly increased in the model control group （P<0.01）.Comparing with the model control group

the renal cortex microcirculation blood flow was significantly decreased in all administration groups（P<0.01）.Comparing with the normal control group

the whole blood viscosity

plasma viscosity and Casson viscosity was increased in the model control group（P<0.01）.Comparing with the model control group

the plasma viscosity was significantly decreased in the kidney-warming spleen-fortifying group （P<0.05）.Conclusion Kidney-warming spleen-fortifying formula can improve the renal function

reduce the blood viscosity and improve the renal microcirculation in DN rats.