The influence of initial strain state on the dynamic response of an end bearing pile embedded in isotropic saturated soil is investigated through the linearized theory of small elastic perturbation superposed on largely stressed bodies.The governing equations for soil,based on Biot’s poroelasticity theory,are derived in the cylindrical coordinates,and the pile is modeled by using the one-dimensional elastic theory.The analytical solutions of pile impedance,frequency response of both twist angle and time history of velocity response are obtained by using of separation of variables technique.Finally,a parametric study of the influence of initial strains on the torsional impedance,twist angle,and velocity response at the top of the pile is carried out. The influence of initial strain state on the dynamic response of an end bearing pile embedded in isotropic saturated soil is investigated through the linearized theory of small elastic perturbation superposed on substantially stressed bodies. The governing equations for soil, based on Biot’s poroelasticity theory, are derived in the cylindrical coordinates, and the pile is modeled by using the one-dimensional elastic theory. The analytical solutions of pile impedance, frequency response of both twist angle and time history of velocity responses are obtained by using of separation of variables technique. a parametric study of the influence of initial on the torsional impedance, twist angle, and velocity response at the top of the pile is carried out.