Advanced model-based control strategies can significantly improve energy conversion efficiency and equipment safety. However, current hybrid wind-wave energy system model can often accurately describe the system response but are complex in structure, and they are more suitable for performance analysis than controller design. In this paper, a dynamic model is proposed, which contains six degrees of freedom (DOFs), the surge, pitch and heave of the floating offshore wind turbine (FOWT), and one pitch for each of the three wave energy conversions (WECs). The model is derived from Newton’s second law so that it has the same physical significance as the real system, and an adaptive algorithm is used to estimate the unknown parameters in the model. The model is validated by AQWA/ANSYS and proved to accurately predict the motion response of the platform under different environmental conditions.