M-current plays an important role in the regulation of neuronal excitability and stabilizing the membrane potential. KCNQ2 and KCNQ3 potassium ion channels are proposed to underlie the neuronal M-current. In this paper, we studied the permeable properties and the selective properties of the KCNQ2/3 potassium channel with molecular biology and electrophysiology methods, respectively. Then, based on the first principle and the structure of the KCNQ2/3 potassium ion channel, the potential curve is calculated by the density functional theory. And forced by the potential, the dynamical properties of KCNQ2/3 channels are also studied. Our results, not only from electrophysiology study but also stochastic dynamics simulations, indicate that heteromeric KCNQ2/3 channels all showed a permeation sequence of K+ >Rb+>>Na+. The aim of this research is looking for a possible physical basis for the permeation of ion channel and opens an avenue for further research.