Background: The development of cardiovascular and cerebrovascular diseases is closely related to geomagnetic activity. The incidence of cardiovascular and cerebrovascular diseases was significantly increased in patients with a history of myocardial ischemia when geomagnetic burst. Myocardial ischemia/reperfusion injury (MI/RI) is the leading cause of death in ischemic cardiovascular and cerebrovascular diseases. Therefore, how geomagnetic activity influence MI/RI become an urgent problem to be solved. Methods: Simulated the strong geomagnetic outbreak, the myocardial ischemia /reperfusion rat model was radiated, the area of myocardial infarction, hemodynamic parameters, creatine kinase, lactate dehydrogenase, melatonin and troponin I in rats were measured after intervened for 24h. Results: Our analysis indicates that the concentrations of troponin I in the geomagnetic shielding-operation group were lower (1.38±0.17*ng/ml, versus geomagnetic radiation-operation group 2.00±0.23 ng/ml, n=3/group, mean± SD, *P<0.05), the concentrations of melatonin in the magnetic shielding-operation group were higher (556.12±44.47*pg/ml, versus geomagnetic radiationoperation group 396.47±27.77* ng/ml, n=4/group, mean± SD, *P<0.01), the CK in geomagnetic shielding-operation group were lower (311.40±4.65*IU/ml , versus geomagnetic radiation-operation group 954.73±44.77IU/ml, n=3/group, mean± SD, *P<0.05). LVDP and ± dp/dtmax in the geomagnetic shielding-operation group were higher (76.82±1.2* mmhg, 3569.09±49.81, respectively, versus geomagnetic radiation-operation group 53.02±1.13 mmhg, 2154.86±42.00, n=11/ group, mean± SD, *P<0.01). There was no significant difference in myocardial infarction area, LVEDP and LDH between the geomagnetic shielding and the geomagnetic radiation. Conclusion: Our data suggests that geomagnetic activity is important in regulating myocardial reperfusion injury. The geomagnetic shielding has a protective effect on myocardial injury and the geomagnetic radiation is a risk factor for aggravating the cardiovascular and cerebrovascular diseases.