AIM: To explore if peroxyntrite （ONOO－) induced iNOS via Fas/ Fas/L pathway in diabetic rats and the effection of cholecystokinin octapeptide-8 (CCK-8) as therapeutic agent for decrease diabetic retinopathy. METHODS: Thirty-six rats were taken as control group, seventy two were given (streptozotocin) STZ (45mg/kg) and then divided into ONOO－group and CCK-8 group (peritoneal injection CCK-8). STZ-induced diabetic rats were treated with CCK-8 for 60 days. Western blotting analysis, DNA ladder, RT-PCR, immunohistochemistry and flow cytometry were used for determining the expression of nitrotyrosine (NT, the foot print of ONOO－); apoptosis and inducible nitric oxide synthase (iNOS) mRNA as well as Fas/Fasl signal transduction in RPE cells. RESULTS: Both RPE cells in ONOO－ and CCK-8 group developed apoptosis and expressed NT, iNOS mRNA and Fas/Fasl. But latter delayed the all changes in a time-dependent manner compared with control and ONOO－ group (P＜0.001). iNOS and Fas/Fasl were up-regulated and associated with an increase of expression of ONOO－in vivo. CONCLUSION: The study suggested that apoptosis of RPE was partly induced by ONOO－ may be the new way of oxidative damage to the RPE cells. CCK-8 decreased RPE cells apoptosis partly induced by ONOO－ and is a potential drug for therapy of diabetic retinopathy. The mechanism of CCK-8 dealing with RPE cells may be related to its direct inhibition of the formation of iNOS to produce ONOO－ and antagnism of damage of ONOO－ to RPE cells.