Abstract: Using analytical method, the problem for torsional vibration of end-bearing pile in saturated soil is studied under the imperfect contact between pile and soil. The imperfect contact of saturated soil layer and end-bearing pile is described by Kelvin model, which is compared with the previous continuity model. Based on Boit’s theory, the dynamic impedance of the saturated soil to torsional vibration of the pile is obtained by Novak’s layer method. The end-bearing pile is treated as Euler-Bernoulli rod mode. The responses of dynamic stiffness factor and equivalent damping of pile top against the frequency are shown in figures. The differences for stiffness factor and equivalent damping at the pile top between imperfect contact and continuity model are analyzed by numerical method. It is shown that when the exciting frequency is large, the vibration amplitude of dynamic stiffness and damping at the pile top under the perfect condition is smaller than it under the imperfect contact. Therefore, it is more reasonable for simulating the contact surface with imperfect contact.