Abstract: Considering the operational and parked states, a generalized single degree of freedom model was established to explore the influence mechanism of wind-wave loadings on the seismic response of offshore wind turbines (OWTs). The statistical relationship between the wind and wave was employed to determine the parameters of the power spectra of the wave. Subsequently, the seismic response of the NREL 5MW OWT was analyzed using FAST to validate the conclusions of the preliminary analysis and evaluate the effects of wind-wave loadings on the seismic response of OWTs. The results reveal that the aerodynamic damping and dynamic loading effects of the wind and wave had a significant influence on the seismic response of OWTs. For wind turbines in the operational state, the support structure is the most dangerous when the mean wind speed of hub-height equals to the rated speed. In addition, the wind-wave loadings reduce the internal force of the mudline and tower-top displacement under the excitation of strong earthquakes. However, they increase the internal forces and displacement amplitudes at these locations while the OWT is excited by a weak earthquake.