Abstract: A dynamic soil model is proposed in this paper. The stress-strain relationships, pore water pressure, seismic subsidence and pile-soil interface are taken into account in the model. In combination with Biot's dynamic consolidation theory, which describes the dynamic interaction of two-phase porous media system, the dynamic analysis of effective stress is conducted to predict the seismic subsidence of pile foundations. The model is utilized to calculate the seismic subsidence of a typical tall building's pile foundation on liquefied soils. Numerical results show that soil liquefaction can lead to large seismic subsidence of pile foundations. It is also found that the transient subsidence of pile foundations is small during earthquakes and the main seismic subsidence is developed for a period after earthquakes.