Objective：To observe the protective effects and mechanisms of hydrogen sulfide（H2S）on isoproterenol（ISO）induced acute myocardial injury in mice. Methods：C57BL/6 mice of 12-week-old were subcutaneously injected with H2S donor NaHS［10 μmoL/（kg·d）］for 2 weeks，and then large dosage of ISO［150 mg/（kg·d）］was jointly given by subcutaneous injection for 2 days. Pathological structures of myocardium were assessed. Activities of creatine kinase（CK）and lactate dehydrogenase（LDH）in plasma were measured. Levels of reactive oxygen species（ROS）and malondialdehyde（MDA），total antioxidant capacity（T-AOC），activity and expression of superoxide dismutase（SOD）in myocardium were detected. Results：NaHS pretreatment improved ISO induced pathological disorder in the myocardium，reduced CK and LDH activity in the plasma，decreased the level of myocardial ROS and MDA，improved myocardial T-AOC，enhanced myocardial SOD activity and expression. Conclusion：H2S alleviated ISO induced acute myocardial injury in mice，which might be associated with the improvement of SOD expression and activity，and the reduction of oxidative stress.