Abstract：【Objective】To investigate the molecular mechanism of abnormal platelet activation induced by platelet O2 ·- and H2O2 levels in type 2 diabetes mellitus.【Methods】The platelet parameters in patients with type 2 diabetic patients and normal controls were measured；Immunofluorescence technique was used to observe the platelet morphology changing；Flow cytometry was used to detect platelet intracellular O2 ·- and H2O2 content in two groups，then with platelets in normal controls treated with NADH/ PMS system and H2O2 respectively，platelet activation positive percentage was observed. Standard Western blot analysis protocols were used to detect expression difference of Catalase and type 2 super-oxide dismutase（Mn-SOD）in platelets.【Results】The MPV in the group of type 2 diabetic patients was significantly higher than in the normal control group（P < 0.001），but there was no statisticdifference in PLT，PDW，PCT between two groups. Immunofluorescence results showed that morphology of platelets in type 2 diabetic patients changed contrast to normal group. Through flowcytometry detection，the content of mitochondrial O2·- and H2O2 of platelet in type 2 diabetic patients were obviously higher than in normal group（P < 0.05），whereas no significant difference in cytoplasmic O2·-. We adopted NADH/PMS system and H2O2 to treat platelets of normal group，heightened activated positive percentage were observed which described O2·- and H2O2 can significantly promote platelet activation（P < 0.01）. Western blot results showed that expression of Catalase in platelet of type 2diabetes patients decreased，while the expression and activity of Mn- SOD had no difference. 【Conclusion】It is diabetic platelet Catalase expression decreased that may lead to Diabetic platelet mitochondrial O2 ·- and H2O2 level increased ，thus regulating aberrant activation of diabetic platelet.