Abstract: In order to study the horizontal seismic response of end-bearing piles in unsaturated soils subjected to SH waves, the free field vibration of soils induced by SH waves is firstly obtained based on the one-dimensional wave theory. Then, considering the dynamic shear modulus of soils to change with saturation, an unsaturated soil-pile coupling vibration model is established by using the three-dimensional continuum mechanics and the Euler beam model. By introducing the potential function and the separation of variables, the expressions for the interaction and amplification factors of horizontal displacement of pile head and the pile curvature ratio are derived, and verified by comparison with the previous research results. Finally, the influences of soil saturation, pile length-diameter ratio and viscous damping of soils on the horizontal seismic characteristics of piles and their variation reasons are discussed. The results show that saturation and pile length-diameter ratio have significant effects on the interaction and amplification factors of horizontal displacement of pile head only in the high frequency range. With the increase of soil viscous damping, the interaction and amplification factors increase and decrease respectively only at the resonant frequency.