Abstract: The offshore structures of single pile foundation may suffer serious damage under seismic action because of the complex marine environment. In order to solve the dynamic response of the pile foundation under seismic action, a simplified analytical solution for water-pile-soil interaction system considering elastic half-space of soil under seismic action is established. Firstly, the pile is assumed to be viscoelastic material, which can be divided into multiple pile segments in the water-pile-soil interaction system. The soil and water are assumed to be linear viscoelastic medium and acoustic medium respectively. Then, based on the Helmholtz decomposition, separation of variables and water-pile-soil continuity condition, the displacement expression of the whole pile is obtained. Then, the analytical solution is degenerated into two cases, and compared with that of the substructure method in the case of soil without water and the rigid analytical solution in the case of soil with water so as to verify the rationality of the elastic analytical solution. Finally, some parameters are analyzed by using this elastic analytical solution to study the influences of three parameters, namely water, soil and pile, on the dynamic response of pile displacement. The research results are of certain reference value for the design of offshore pile foundations.