To study the protective effect of Zhenhu granules for myocardial ischemia injury induced by isoproterenol(ISO)in rats.Methods：Divided 32 healthy SD rats into the blank group，the model group，the low dose group and the high dose group randomly，with 8 cases in each group，and adaptively fed them for 7 days.The low and high dose groups were given Zhenhu granules by gavage according to the conversion amount of the body surface area of rats，and the blank group and model group were given normal saline of the same volume once a day for 14 consecutive days.30 min after the last gastric perfusion，recorded II lead electrocardiogram of anesthetized rats in each group；the model group，the low and high dose groups were given subcutaneous injection of ISO and established the myocardial ischemia model.The blank group was given normal saline of the same volume once a day for 2 consecutive days.Respectively recorded the electrocardiogram 30 min later and 12 h after the last subcutaneous injection of ISO，observed the changes of J point of electrocardiogram.After recording the electrocardiogram collected the blood from the abdominal aorta of rats in each group，detected the levels of serum creatine kinase(CK)creatine kinase isoenzyme(CK-MB)and lactate dehydrogenas(LDH)after centrifugation and took myocardium of heart apex of rats in each group for HE staining and observed the degree of myocardial ischemia damage.Results：Compared with that in the blank group，the displacement of J point in the model group significantly was increased in 30 min after ISO injection and in 12 h after the last subcutaneous injection of ISO(P ＜ 0.05)；serum CK，CK-MB and LDH were all significantly increased(P＜0.05).Compared with that in the model group，the displacement of J point of the high and low dose groups of Zhenhu granules was significantly reduced in 30 min after ISO injection and in 12 h after the last subcutaneous injection of ISO(P ＜ 0.05)；serum CK，CK-MB and LDH were all significantly reduced(P ＜ 0.05)；there was no significant difference being found in the comparison between the low and high dose groups.HE staining indicated that there was apparent damage on myocardial cells in the model group，while the damage of myocardial cells in the low and high dose groups was reduced when compared with that in the model group.Conclusion：ISO can induce ischemic changes in the electrocardiogram of rats，increase the myocardial enzymes and lead to myocardial ischemia injury.The application of Zhenhu granules has obvious protective effect on ischemic myocardium.