Abstract: The excess pore water pressure in saturated sands was controlled by applying the back pressure to the stratum, which was used to simulate the saturated sand with the residual pore water pressure under seismic loads. Model tests of the soil-pile interaction were conducted to research variations of p-y curves of saturated sands with different states with an increase of the residual pore water pressure. Research results showed that the ultimate lateral resistance and the subgrade reaction modulus coefficient can be determined based on strength parameters of saturated sand with residual pore water pressures. p-y curves of saturated sands were further determined under seismic loads.