Objective To study protective effect of Dingxin Formula on arrhythmia rats with myocardial ischemical reperfusion injury and its effect on NF-κB activation.Methods Coronary artery was ligated and loosened again to establish arrhythmia rat models with myocardial ischemical reperfusion injury.Arrhythmia was scored by electrocardiogram.Pathological change and expression of NF-κB in myocardium were observed by HE stain and immunohistochemical method respectively.Results Dingxin Formula could reduce arrhythmia with ischemical reperfusion injury（P<0.01）and pathological change in myocardium

and decrease the expression of NF-κB significantly（P<0.01）.Conclusion Dingxin Formula has a protective effect on arrhythmia rats with myocardial ischemical reperfusion injury by inhibiting NF-κB activation.