According to the characteristics of liquefiable soil in earthquake, we divide the liquefiable soil layer into a top liquefied layer and a bottom nonliquefied layer. Based on the Winkler model for the pilesoil interaction and treating the pile as a Rayleigh beam, the governing equations and the corresponding boundary conditions for interaction of the single pilesoilsuperstructure are established. This is done by taking into account the mass and inertia moment of the superstructure, and the inertia moment and the axial force of the pile. A closedform solution is obtained in the frequency domain, of which results are in agreement with experiments. Influences of the geometrical and physical parameters on the displacement amplification factor and the dynamic amplification factor are investigated. It is shown that the axial force drives the first natural frequency of the system to approach the dominant frequency of earthquake. Soil liquefaction increases the system’s dynamic response, and the critical load of the pile decreases with the degree of soil liquefaction, leading to unstable failure of the pile.