Objective  To observe the protective effect of Xinmailong injection (XML) on myocardial ischemia reperfusion (I/R) injury in rats model.    Methods  The levels of SPF 60 successful acute myocardial ischemia rat models were randomly divided into control group,I/R group and XML group(Different drug concentrations 50 mg/L,100 mg/L, 200 mg/L, 400 mg/L). The control group was continuously given K-H nutrient solution for 2 hours, the other group was given respective different drug concentrations or K-H nutrient solution by Langendorff isolated heart perfusion method  after ischemia 30 minutes.The following indicators were detected: Hemodynamics included heart rate (HR), left ventricular development pressure (LVDP) and ±dp/dtmax; the myocardial enzymes included creatine kinase (CK), creatine minase-MB (CK-MB), troponin-Ⅰ (Tn-Ⅰ) and myoglobin (MYO), coronary flow and myocardial infarct size were observed. The expression of Bax and Bcl-2 in each group was detected by Western blotting and immunofluorescence.    Results  Xinmailong injection could alleviate LVDP and ±dp/dtmax; decrease the release of CK, CK-MB, Tn-Ⅰ, MYO and the shrink area of myocardial infarction; increase the coronary flow; enhance heart rate fast and certain inhibition of myocardial apoptosis.    Conclusion  Xinmailong injection can alleviate the damage of cardiac function caused by myocardial ischemia/reperfusion injury.