Objective To evaluate the protective effect and mechanism of luomaishutong(LMST)on acute myocardial ischemia-reperfusion injury in rabbits.Method Twenty-four New Zealand white rabbits were randomly divided into 3 groups:the LMST group,the control group and the sham-operated group.The AMI reperfusion model was established by removing the blockade after the occlusion of coronary artery for 2 hours.The changes of hemodynamics,oxygen free radical and clearance system were measured in all rabbits.Results (1)Compared with the control group,left ventricular systolic pressure(LVSP)and maximal changing rate of left ventricular innner pressure(?dp/dt_(max))increased remarkably in the LMST group after reperfusion,meanwhile, LVEDP decreased significantly.(2)In the control group,MDA level of cardiocyte was noticeably higher,while SOD and NOS levels were lower than in the sham-operated group.Compared with the control group,MDA level in the LMST group was significantly lower.Furthermore,SOD and NOS levels were higher in LMST group,and the infarcted area was smaller in the LMST group as well.Conclusions LMSF can protect myocardium after ischemia-repcrfusioninjury and improve cardiac function through inhibiting induced by oxygen free radicals.