Abstract:The key issues in design of deep-sea large-megawatt floating offshore wind turbine structures are focused in this paper. The floating supporting structure applies the OC3Spar platform of the National Renewable Energy Laboratory (NREL) as the benchmark model. The 5MW, 6.7MW and 8MW wind turbines are selected respectively, and the corresponding floating supporting structure design is proposed using the scale factor design method. Considering the combined wind load and wave load, the hydrodynamic analysis and strength analysis of the floating support structure under operating conditions and extreme conditions were carried out, and the amplitude response operator(RAO) of the support structure and the stress response of the critical nodes of the structure with the power of the wind turbine were obtained. An improved design for reducing the stress of the critical nodes is proposed and the results show the validation of the design.