Objective To investigate the therapeutic effects and mechanisms of tetramethylpyrazine (TMP) on streptozocin(STZ)-induced-nephropathy in type 2 diabetic rats. Methods 50 SD rats were randomly divided into normal group(n=10) and model group(n=40). The model rats were fed on high fat and sugar diets for 4 weeks, then given STZ(40 mg/kg,ip). After 72 hours, the fasting blood glucose (FBG) was measured. Rats with high FBG above 16.67mmol/L were randomly divided into four groups: model, metformin(Met, 250 mg/kg)and TMP (80 mg/kg, 160 mg/kg) groups for treating 8 weeks, and both the control and model groups were given equals distilled water by intragastric administration. At the end of the experiment, blood glucose, urine protein, blood urea nitrogen and creatinine were measured. The expression of TLR4 and caspase3 protein in kidney tissue of rats was determined by immunohistochemistry. Pathological changes of kidney were observed under light microscope. Results Compared with the model group, metformin and high dose of TMP administered after 8 weeks, rats can significantly reduce the dynamic fasting blood glucose(P<0.05). Urinary protein excretion of total dynamic decreased significantly (P<0.01, P<0.05); the protein expression of TLR4 and caspase3 in the metformin group and high dose group was significantly lower than that in the model group (P<0.05); kidney tissue pathological damage was significantly reduced. Conclusion TMP has a protective effect on STZ induced nephropathy in type 2 diabetic rats, and its mechanism may be related to the down-regulation of TLR4 expression.