Objective To observe the effects of blocking renin-angiotensin system with losartan or perindopril on renal angiotensinⅡand its type 1 receptor （AT1R） expression in STZ-induced （diabetic） rats. Methods Male SD rats were randomly divided into 2 groups: normal control group （NC） and （diabetic） group. Diabetes was induced by STZ （65 mg/kg） abdominal injection. Four weeks later, diabetic rats were further divided into 4 groups: diabetic rats treated with losartan (DL, 20 mg·kg-1·d-1),diabetic rats treated with perindopril (DP,2 mg·kg-1·d-1) and diabetic untreated control group（DC）. Radioimmunoassay was used to measure plasma and renal angiotensin （Ⅱ.）Expression of AT1R was detected by RT-PCR in each group before and after 12 week′s treatment. Results At the 4th week, renal AT1R expression decreased. At the 16th week, plasma angiotensinⅡ,renal angiotensinⅡand AT1R mRNA in diabetic untreated group were significantly higher than those in normal rats. （Renal） angiotensinⅡand AT1R in losartan or perindopril-treatmented group were significantly lower than those in DC group. Conclusion Intrarenal RAS is abnormal in STZ-induced diabetic rats. Renoprotective effects of losartan and perindopril may partly induced by inhibiting renal angiotensinⅡ and AT1R （expression.）