Abstract: The antiarrhythmic activity of Guanfu base A (the main active prinple obtained from the tuber of Aconitum coreanum (Levl.). Raipaics was investigated in animals. It was evident that the aconitine-induced ventricular arrhythmia in rats, the electrical stimulation-induced ventricular fibrillation in rabbits and the oubain-induced ventricular tachycardia in dogs could be protected or arrested by Guanfu base A intravenously. The dose thresholds required for ventricular premature beats, ventricular tachycardia and ventricular fibrillation in rats during intravenous infusion of aconitine at constant rate were all raised by the premedication of Guanfu base A . The Guanfu base A could lower the heart rate, prolong P-Q,Q-T interval, but had no any effect on QRS waves. Its effect of slowing heart rate could not he blocked or antagonised by atropine and isoprenaline.