Abstract: In this study, a numerical simulation framework named ABAQUS-FAST (A-F) is developed by combining the commercial finite element software ABAQUS with the open-source wind turbine analysis tool FAST. This approach enables the dynamic analysis of floating offshore wind turbines (FOWTs) under the simultaneous influence of aerodynamic loads, hydrodynamic forces, servo control actions, and earthquake excitations. The aerodynamic loads are modeled using blade element momentum (BEM) theory, while wave- and earthquake-induced hydrodynamic forces are evaluated based on potential flow theory. Hydrostatic restoring forces are simulated using linear spring elements, and mooring line behavior is represented with tension-only elements. A detailed numerical model of the NREL 5 MW semi-submersible wind turbine is established to examine the response of key structural components under various environmental loading scenarios, including different wind speeds, wave parameters, and ground motion characteristics. Results show that wind and wave forces are the primary contributors to significant platform motion, particularly near rated wind speed conditions. Earthquake loading intensifies tower-top displacements, with long-period earthquakes inducing stronger responses due to their concentrated energy spectra. Moreover, wind and wave actions can mitigate the earthquake effects on the tower to some extent, while earthquake loading markedly increases mooring line tension variations. Vertical earthquake motion is also found to trigger considerable additional horizontal responses. The outcomes of this work provide a technical reference for the safety assessment and design optimization of FOWTs under multi-hazard conditions.