Abstract: Objective To elucidate the role of nuclear factor kappa B （NF-кB） in early phase of myocardial ischemical reperfusion injury. Methods Eighteen goats were randomly divided into three groups：extracorporeal circulation group（CPB group）, ischemical reperfusion group （IR group） and ischemical reperfiision plus pyorrole dithitocarbamate group （PDTC, a special inhibitor of NF-kB activation）. Goat hearts were subjected to 60 minutes of ischemia, followed by 90 minutes of reperfusion（the inhibitor team goats were administered with PDTC before cardiac arrest）, then hemodynamics of data and cardiac function was measured. Cardiomyocyte apoptosis index was determined by Tdt-mediated dUTP nick end labeling and NF-kB binding activity in the nucleus was measured by electrophoretic mobility shift assay （EMSA） analysis. Results Ischemia/reperfusion could lead to typical histological change of myocardial ischemic injury, while NF-kB was obviously activated in the ischemic injury. The levels of NF-kB binding activity in the myocardium increased signifficently in contrast to isolated extracorporeal circulation group （P＜0.05）. However, 60 minutes or 90 minutes after reperfusion, the levels of NF-kB binding activity in ischemic reperfusion with pyorrole dithitocarbamate group and the histological change of myocardial ischemic injury reduced signiflcently. Apoptosis index of the ischemic myocardium from IR and PDTC groups was 11.2%±0.4% and 6.35%±0.2% respectively （P＜0.05）. Conclusions Nuclear factor-KB plays an essential role in the early phase of myocardial ischemia/reperfusion injury, PDTC reduces myocardial ischemia/reperfusion injury by inhibiting activation of transcription factor NF-kB.