Abstract: OBJECTIVE To study the influence of Oxytropis falcate Bunge on the content of NO, and the activities of NOS and iNOS in myocardial ischemia and reperfushon injury rats to explore its possible protective mechanism in vivo. METHODS The model of myocardial ischemia reperfusion injury in rats was employed by ligating the artery of left anterior descending. After the following reperfusion for 40 minutes, the concentration of NO and the enzymatic activities of NOS, iNOS in rats’ myocardial tissue were tested. RESULTS The results showed that the enzymatic activities of NOS, iNOS and the concentration of NO of myocardial tissue in ischemia-reperfusion model group were much higher than that of normal control group. The enzymatic activity of NOS, iNOS and the concentration of NO of myocardial tissue in test groups were lower than that of model group. CONCLUSION Oxytropis falcate Bunge plays protection effects during acute myocardial ischemia-reperfusion injury in rats in vivo by decreasing the enzymatic activity of NOS, iNOS and the concentration of NO.