Objective To explore the effects of telmisartan on the kidney function in diabetic rats and to investigate its possible mechanism. Methods SD rats were randomly divided into two groups:diabetic group (n=20) and control group (n=10). The diabetic group was injected with streptozotocin (STZ). Diabetic rats were randomly divided into two groups:telmisartan group (treated with 10 mg/kg/d telmisartan, n=8) and diabetic group (n=8). The fasting blood glucose, body weight, 24-hour urinary protein, creatinine clearance rate (Ccr), serum creatinine and blood urea nitrogen (BUN) were tested. Gene expression in the rat renal tissues was assyed with microarray analysis. ResultsTelmisartan significantly decreased 24-hour urinary albumin (P<0.01), serum creatinine (P<0.05), BUN (P<0.01), and increased Ccr (P<0.05), compared with those of the diabetic group. Microarray analysis showed that expressions of 1541 genes were significantly changed in the telmisartan group (554 increased, 987 decreased). Real-time PCR verified that ATP synthase beta subunit (ATP5b), cytochrome c oxidase subunit Vic (Cox6c), and NADH dehydrogenase (ubiquinone) Fe-S protein 3 (Ndufs3) were significantly down-regulated. Conclusion Telmisartan can improve kidney function in diabetic rats. Mitochondria oxidative phosphorylation and PPAR-γ pathway may be involved in the mechanism of action.