[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 O 2 ·- and H2O2 level increased ,thus regulating aberrant activation of diabetic platelet.