The influence of mooring chain pretension of wind turbine on motion response characteristics is researched through time domain coupling analysis method, with a 6 MW offshore single column floating wind turbine as the study object. The numerical simulation results show that increasing the mooring chain pretension could effectively improve the surge and heave motion of the wind turbine, while has limited influence on the pitch and roll motion. According to the influence of mooring chain pretension of the wind turbine on motion response characteristics, the mooring system is optimized, which could ensure the safety of the floating wind turbine and enable the floating wind turbine to have a good overall motion response. The conclusions will provide some reference for the design of floating wind turbine mooring system.