Abstract: To investigate the protective mechanism of oleuropein on the kidney of diabetic rats, male SD rats were divided into normal control group, diabetic model group, oleuropein treated group and positive benazepril control group based on their body weights. The diabetic animal model was made by a single intraperitoneal injection of65 mg / kg streptozotocin ( STZ) .One week after successful modeling, the diabetic rats were treated with oleuropein or positive benazepril for seven weeks, and then indexes of their urine, blood and kidneys were measured.Results:Compared with diabetic model group, the oleuropein treated rats showed significant decrease in levels of renal index, blood glucose, blood lipid, serum Scr, BUN, UA, UALB, UAER and MDA, increase in levels of serum Ig G, Ig M and complement C3, C4, telomerase, SOD and CAT, and reduce in content of MDA. Meanwhile, the use of oleuropein resulted in decrease of expression of TGF- β1 and Smad4 in diabetic rats. These results indicated that oleuropein had a protective effect on the STE- induced renal tissue injury in diabetic rats, due to enhancing renal antioxidant capacity, telomerase activity and immune function, as well as inhibiting expression of TGF- β1 and Smad4.