Abstract: Based on the Novak’s thin layer element method and the theory of radiant stresses, the radiation stress solution to the displacements of pile and soil in the Laplace domain is derived. The potential function is introduced to decouple the governing equation for soil considering the mixed boundary conditions on the pile-soil interface. The Durbin algorithm and the accelerated convergence algorithms of Laplace numerical inverse operation are used to resolve the transient response in time domain. Compared with those of the continuous solution, finite element and boundary element methods, the validity and reliability of the radiation stress solution are verified, and the influences of the local separation characteristics on the dynamic response of the pile and the soil are analyzed. The parametric studies are carried out, and the effects of the modulus ratio of pile and soil and the slenderness ratio of pile on the transient response of pile under horizontal impact loads are studied. It is shown that the local separation characteristics of the pile-soil interface have a significant influence on the magnitude of the pile displacement and the distribution of the displacement field of the soil around the pile. Moreover, it has certain influences on the variations of displacement response of pile under different modulus ratios between the pile and the soil. The displacement of pile is significantly affected by the modulus ratio and also greatly affected by the slenderness ratio when the value of slenderness ratio is small.