The theory of ion transport for three-barrier model is developed which takes into account the limited number of sites in the one-dimentional channel. The case of single kinetic barrier is considered, that corresponds to the ion transport through the sodium channel of biological membrane. The reversion potential, conductance and fluxes are calculated. The results show that the independence principle in the case of channel-induced transport is not valid, but [ Ussing's relation remains valid. Al measurable quantities of the channel depend on two-parameters: partition coefficient K and kinetic contant υ. The comparison of Hille's experimental data, for Tl +, aminoguanidine and other substituting ions, with the theory provides all parameters and an interpretation of experimental findings.