Abstract: Guan-fu base A(GFA)is a terpenoid alkaloid isolated from the tuber of Aconitumcoreanum in our institute. GFA(20～30mg·L^-1) reduced the ventricular tachycardia(VT)andventricular fibrillation(VF) rate induced by K⁺-free and high Ca²⁺ solution in Langendorf heart ofrats. Pretreatment of conscious rats with GFA 2.5～10 mg· kg^-1 iv, increased the amount ofbeiwutine necessary to preduce arrhythmias. Ouabain-induced VT in conscious dogs was reverted tosinus rhythm in 1～2min by iv GFA 9～10 mg· kg^-1. GFA 10～20 mg·kg^-1 iv was also foundto be effective in protecting anesthetized dogs from atrial fibrillation induced by topical application of ACh. GFA 10 mg·kg^-1 iv obviously decreased heart rate and prolonged the P-R interval,but slightlyaffected the myocardial contractility in anesthetized dog GFA showed no obvious effect on strokevolume and cardiac output in conscious dogs.In conclusion, GFA showed therapeutic and prophylactic effect on different models ofexperimental arrhythmias without causing marked effect on myocardial contractility.