In order to study the seismic response of offshore monopile wind turbine, the FLAC3D is used to establish the overall structural model of offshore wind turbine on liquefaction-containing interlayer foundation, and the pile-soil and pile-seawater coupling is considered. Soil liquefaction and structural internal deformation under earthquakes of different intensities were simulated, and the effect of seawater depth was analysed. The results show that: soils are more susceptible to liquefaction in the shallow layer. The size of the liquefaction area, the deformation of the structural are directly proportional to the peak ground acceleration; The liquefaction of the soil produces a significant increase in the structural deformation. The influence of the change of water depth on the pile body is mainly reflected in the submerged section, the increase of water depth makes the length of the pile subjected to dynamic water pressure in the submerged section increase, which leads to the increase of displacement and internal force at the top of the pile.