Abstract: This paper presented motion responses of the floating VAWT (vertical axis wind turbine) considering the coupling between aerodynamics and hydrodynamics, the method of aerodynamics of fixed VAWT was improved to calculate the aerodynamics of the floating VAWT. The equations of surge, heave and pitch motions of the floating VAWT were established considering the damping forces, wave forces, wind loads, mooring forces, and so on. The formula of wind loads acting on the blades were deduced by the double-multiple-stream tube theory considering the dynamic stall and motions of the floating foundation, and a computing code was developed. Taking the Sandia 17 m wind turbine as an example, the validity of the aerodynamics computing code was verified. The model tests were carried out, where the wind turbine is Φ-Darrieus type and the foundation is truss Spar type. The results obtained by the model tests were compared with those obtained by the numerical simulation, and the coupling computing code was verified.It is found that, the RAO (response amplitude operator) curves of heave and pitch motions of the floating VAWT obtained by numerical calculation agree well with those obtained by model tests, and the validation of the coupling computing code was verified. However, there is difference between the results of numerical calculation and the model tests. This is because the differences between the numerical model and the model tests, mainly regarding the degrees of freedom of the floating VAWT motions, the damping, and the wind forces.