Abstract: PTS is a component part of Panax notoginseng (Burk) F. H. Chen. Chemical analysis showed that it consisted of two single component—saponins of Panax notoginseng C₁ and D₁.The iv LD₅₀ of PTS was found to be 3806±143 mg/kg in mice.It showed antiarrhythmic effects on aconitine or BaCL₂ induced arrhythmiasi rats and on adrenaline induced arrhythmias in rabbits.PTS was shown to alter the ECG in anesthetized rats and prolong the R-R, P-R and Q-T_c interval. The electrophysiological effects of PTS on the guinea pig papillary muscle cells were studied using intracellular microelectrode. The results showed that the APD and ERP of myocardial cells were prolonged and SP₂ was decreased after perfusion with PTS of 62.5 μg/ml.The results suggest that PTS had a significant antiarrhythmia effect. Th mechanism of action may be similar to that of amiodarone, that is, direct inhibition of the myocardia, prolongation of APD and ERP and non-competitive antagonization of the β-adrenergic receptor.