Abstract: Based on the finite element method and the theory of mode superposition,a quasi-static calculation method for the seismic response of rigid pile composite foundation under SV wave is presented.The nonlinear behavior of the soil is considered by the equivalent linear method,and the influence of the inertia force of the super-structure and the deformation of the free field response on the internal force of the pile is considered separately.The former is analyzed by using the mode superposition method of response spectrum,and the latter is analyzed by using a modified FEM for seismic deformation of underground structures.It is found that both the peak values and the distribution of the force in the pile can be calculated satisfactorily by using the method proposed,and that the efficiency of calculation is greatly increased.