For the DTU 10MW wind turbine, a new type of semi-submersible wind turbine foundation without transverse brace is designed, and by adjusting the basic ballast, the foundation is equipped with DTU 10MW and NREL 5MW wind turbines, respectively. On this basis, the commercial software SESAM/SIMA is used to establish a pneumatic-hydrodynamic-servo-elastic fully coupled numerical model. For the two typical working conditions of normal operation and extreme conditions, the time-domain fully coupled calculation of the motion responses of the above-mentioned turbines is carried out. Based on the calculation results, the sensitivity analysis of the overall motion performance of the floating wind turbines to different wind turbine powers is carried out. The research shows that: the motion response of the 10 MW wind turbine is larger than that of the 5 MW wind turbine under normal operation conditions due to the influence of wind excitation; under extreme conditions, the natural period of the pitch of the 5 MW wind turbine is closer to the wave period, resulting in a larger pitch motion than that of the 10 MW wind turbine.