Methoxyadiantifoline ( MAF) is a new alkloid isolated from Thalictrum Omeience W.T.Wang.During 3 min reperfusion after 10 min of coronary ligation, MAF 5 ?mol/L significantly decreased the incidence of isolated rat hearts with ventricular arrhythmias ( VF and VT ) . It delayed the onset of ventricular fibrillation and shortened its duration and markedly prolonged the time of normal sinus rhythm. It also significantly decreased the release of LDH from the myocardium in isolated rat hearts. In addition , MAF 5 ?mol/L could decrease the heart rate and coronary resistance. The results suggest that MAF possessed protective effects on the reperfusion injury in isolated rat hearts.