In the present study, we investigated the interaction of Kv4.2, a voltage-gated K+ channel abundant in cardiac cells, with BmP02, a peptide with 28 amino acids from the Chinese scorpion Buthus martensi Karsch. Although BmP02 hardly exert any inhibition on the maximum current and the voltage-dependence of activation and inactivation of Kv4.2, it could dose-dependently slow down the inactivation of the channel. A slowing of channel deactivation can also be detected upon application of 3 μM BmP02. In addition, the recovery of Kv4.2 from inactivation was accelerated by BmP02 at micromolar concentrations. These findings indicated that the interaction model of BmP02 and Kv4.2 is different from some classic K+ channel toxins such as ChTX and Sharker channel, in which ChTX is often described as a cork into the pore without bringing about any conformational changes to the interaction site. The effect of BmP02 was similar to that of α-toxins such as BmK I which could slow the inactivation phase of voltage-gated sodium channels, suggesting that functional commonality might exist between different types of ion channels, toxins and their interactions. This study may provide a better understanding for the structure-function relationship between Kv channels and toxins.