The potential threat to offshore structures in zones of active seismicity is caused by combined earthquake and wave action. In this paper，the dynamic response of a cylinder structure under the combined action of earthquake and wave is studied by taking the water-structure-soil interaction into account. The flexible column structure is discretized as the Euler beam unit by the finite element method，water-cylinder interaction is replaced by the added mass，and soilcylinder interaction is replaced by the linear spring. Based on the analysis of natural vibration frequency，the influence of soil-structure and water-structure interactions on the natural vibration frequency of the structure is analyzed. The effects of soil-structure interaction，seismic hydrodynamic force and wave force on the dynamic response of the submerged cylinder are investigated.