To study the ischemia/reperfusion-induced dynamic changes in PLA 2 in cardiomyocytes and its effect on phospholipids of cardiomyocyte membrane during cardiopulmonary bypass (CPB), and to evaluate the protective effects of two kinds of cardioplegia. The results showed that there was an increase in PLA 2 activity during CPB followed by decreases in the contents of total phospholipids, phosphatidylcholine and phosphatidylethanolamine. During the 6o-min aorta occlusion beriod,there were no obvious changes in the activity of PLA 2 and the contents of total phospholipids, phosphatidylethanolamine and phosphatidylcholine when cardioplegia was used. During early reperfusion, there were a rapid increase in PLA 2 activity accompanied by a rapid decrease in contents of phospholipids.However,after 30~60min reperfusion, the contents of phospholipids for group C, D began to increase and the PLA 2 activity began to decrease. The changes in the contents of phospholipids and the PLA 2 activity in extracorporeal circulation with warm blood cardioplegia group were smaller in magnitude. These results suggested that the myocardial membrane injury was dependent on PLA 2 activation. Warm blood cardioplegia could provide better myocardial protection, and warrant further improvements.