Through the developed FEM model of pile-soil coupled system with two-phase saturated soil foundation,the seismic simulation of a saturated free field and a pile structure are carried out in this paper.The results indicate that the distribution of excess pore water pressure shows exponential attenuation pattern from ground surface,the soil near the ground surface more tends to be liquefied and loses bearing capacity.Along with the rising of excess pore water pressure and the corresponding degradation of soil strength,the saturated free field shows obvious selective filtering of the high-frequency components in earthquake wave.In the seismic response of pile structure,owing to the coupled pile-soil interaction,the surrounding soil more tends to be liquefied.The decrease of foundation’s bearing capacity leads to larger seismic response and bending moments of structure piles.The conclusions derived in this paper agree with practical engineering experiences,and the numerical method and conclusions could provide some guidance for seismic design of structures in liquefiable saturated soil foundation.