Abstract:  The critical factors controlling structural design of semi-submersible platform are structural categories and design principles, norm formula scantlings design, global structural strength design, local structural strength design and tank structural design, etc., which are studied in this paper. The design methods and requirements can refer to the rules and standards of relevant classification society. The structural design process for semi-submersible platform is also summarized accordingly. This research has certain guiding significance for the structural design of semi-submersible platform.