Aiming at the complex water-pile-soil interaction problem of the single-pile foundation of offshore structures under dynamic loads，this paper establishes a three-dimensional water-pile-soil fully coupled dynamic finite element analysis model. The soil，pile and water are simulated by the solid elements and acoustic media，respectively. The truncation boundary of soil is simulated by roller boundary condition and the truncation boundary of water is adopted by non-reflective absorption boundary condition，and the reasonable truncation boundary position is determined. Then the calculation results of the full coupling analysis model are taken as the reference solution，the effects of four kinds of dynamic load on the displacement and hydrodynamic pressure response of the pile and seabed surface with the water-pile decoupling and water-soil decoupling are systematically studied，and the influence of soil thickness，water depth and pile radius is also discussed.