AIM:To explore the mechanism of angiotensin converting enzyme inhibitor(ACEI)-benazepril(BZ) on the protection of diabetic retinopathy.METHODS:Streptozotocin(60mg/kg)was intraperitoneally injected to establish the diabetic model in 24 male SD rats as experimental group,model rats were divided into diabetes mellitus(DM) group and benazepril(BZ) group,control group was also established.BZ was given to treatment group at dose of 10mg/kg per day by gavage.24 weeks later,plasma angiotensin Ⅱ was detected and immunohistochemistry,Western blot were used to assess the expression of VEGF protein in retina.The changes of basement membrane thickness(BMT) of retinal vessels were observed by transmission electron microscopeRESULTS:The level of plasma angiotesin Ⅱ and retinal VEGF protein expression were significantly higher in DM rats than in control groups and showed a significant reduction in BZ treated diabetic rats(P<0.01).BMT of retinal vessels increased in DM rats and extenuated in BZ treated diabetic rats.CONCLUSION:BZ can reduce retinal VEGF protein expression by inhibiting the level of plasma angiotensin Ⅱand ameliorate BMT of retinal vessels in DM rats.