Objective：To study the role of melatonin and vitamin E in protecting bladder tissues of diabetic rats from oxidative stress injury and complications caused by the imbalance between oxidants and antioxidants. Methods：Diabetic rat models were established through lumbar injection of streptozotocin and the rats were divided into three groups：diabetic control group，vitamin E treatment group and melatonin treatment group. Besides，another normal control group was brought in the experiment. Vitamin E（50 mg/kg） and melatonin（2 mg/kg） were respectively given to rats in vitamin E treatment group and melatonin treatment group. Rats in diabetic con－trol group and normal control group received 4% ethanol physiological saline with a dosage of 2 ml/kg once daily. After four weeks’ injection，changes in ultrastructures of the samples were observed by electron microscope and changes in malonaldehyde（MDA），glu－tathione（GSH） and superoxide dismutase（SOD） of the bladder samples were measured. Results：Results of electron microscope of di－abetic control group showed that mitochondrias of smooth muscle cells，vessel endothelial cells and mechanocytes were swelling and cavitating and thrombus-like structure was observed，which was much milder in vitamin E treatment group and melatonin treatment group than in diabetic group. Compared with those in normal control group，MDA of diabetic control group was distinctly elevated（P<0.01），while GSH（P<0.01） and SOD（P<0.01） were markedly lowered. After treatment with vitamin E and melatonin，MDA was obvi－ously declined（P<0.01），GSH（P<0.01） and SOD（P<0.01） were strengthened. Effects of melatonin on decreasing MDA and in－creasing GSH were much stronger than those of vitamin E（P<0.01），while there was no significant difference in enhancing SOD activity between melatonin and vitamin E（P=0.512）. Conclusions：Melatonin and vitamin E could regulate oxidative stress in the bladder tissues of diabetic rats and protect the mitochondrias of smooth musle cells，vessel endothelial cells and mechanocytes. The protective effect of melatonin is stronger than that of vitamin E.