Spar floting wind turbine is the main infrastructure form of offshore floating wind turbines, and the hydrodynamic performance of Spar structure is an important indicator of its safety. Accurate calculation of the nonlinear hydrostatic restoring forces is important for the hydrodynamic performance. In this study, a typical 6MW Spar floating wind turbine was used as a representative to analyze and calculate the nonlinear hydrostatic restoring coefficient at different inclination angles, and the results obtained by AQWA were verified. The time domain analysis method was adopted, considering the nonlinear hydrostatic restoring coefficient, the time domain analysis of the Spar floating wind turbine was carried out by the self-programmed software, and the results were compared with the hydrodynamic response calculated in the self-programmed software, and the hydrodynamic characteristics and the influence of hydrostatic nonlinearity were analyzed.