Objective:To observe the action of hydrogen peroxide(H2O2) inducing cardiomyocytes over-oxidation injury and to investigate the expression of HMGB1 in apoptosis and necrosis of myocardiocyte. Methods:A model for primary culture of cardiomyocytes injuried by H2O2 was established, the morphology of cardiomyocytes was observed, and cardiomyocytes fraction surviving were measured. The activity of lactate dehydrogenase(LDH), superoxide dismutase(SOD),HMGB1 were assayed. Results: Cardiomyocytes survival rate decreased by H2O2 treatment(P < 0.05), and the activity of LDH increased(P < 0.05),whereas the activity of SOD decreased(P < 0.05). Expression of HMGB1 in H2O2 group A was the same as that in control group, whereas the expression of HMGB1 in H2O2 group B was higher than that in control group and H2O2 group A. Conclusion:The HMGB1 expression increased in the necrosis of cardiomyocytes, while it had no change in the apoptosis of cardiomyocytes.