Abstract: The foundation of a semi-submersible floating plating is the key to ensuring the normal operation of the floating offshore wind turbine, and the design of the dimensions of each component of the plating is particularly important. For a semi-submersible floating platform with large floating tanks structure. Three platforms with different sizes of buoyancy tanks are proposed. To establish three finite element models, stability analysis, hydrodynamic analysis, and strength analysis were conducted to compare and analyze the results with the specifications and standards, and finally determine the platform size. The calculation results show that the size of the buoyancy tank affects the natural periods of heave and pitch of the platform, and the initial stability height decreases as the size increases. The platform with a width of 9 m of the buoyancy tank has relatively good stability and hydrodynamic performance, and its overall strength analysis results also meet the specification requirements.