Abstract: Human ether-a-go-go-related gene (HERG) encodes the rapid component of the cardiac delayed rectifier K⁺ current, which has an important effect on both proarrhythmia and antiarrhythmia. To investigate the effect of sophocarpine (SC) on HERG channel stably expressing in human embryonic kidney-293 (HEK293) cells, whole-cell patch-clamp technique was used to record HERG current and kinetic curves. As the result, it was found that SC inhibited HERG current in a concentration-dependent manner (10, 30, 100, and 300 μmol·L^-1). At 0 mV, 10, 30, 100, and 300 μmol·L^-1 SC respectively inhibited I_HERG by I_step (10.7±2.8)%, (11.3±5.5)%, (47.0±2.3)% and (53.7±2.5)%, and I_tail (1.1±3.0)%, (17.1±3.3)%, (32.7±1.9)% (P<0.05, n=12) and (56.0±2.4)% (P<0.05, n=13). The time constants of inactivation, recovery from inactivation and onset of inactivation were accelerated. SC did not change other channel kinetics (activation and deactivation). It is concluded that SC inhibited the transfected HERG channels by influencing the inactivation state, which is the probable anti-arrhythmic mechanism.