The design of steel–concrete composite columns for 20 MW-scale floating wind turbines remains in the exploratory stage, with unclear load-bearing mechanisms and limited theoretical and regulatory guidance. In this study, a static finite element analysis of the ultimate load-bearing capacity was performed for the world’s first 20 MW steel–concrete composite floating wind turbine column. Based on strength theory, the internal force distribution and crack evolution of the column were investigated. The results show that the composite cylindrical structure exhibits distinct primary bending-moment-dominated behavior. When the load reached approximately 7% of the design limit, localized concrete in the stress concentration zone connecting the cross-deck slab and the steel platform began to cease contributing to load resistance. As the load increased to the design limit, the maximum crack width was about 0.11 mm, satisfying the allowable limit. The study elucidates the internal force characteristics, crack propagation process, and overall deformation behavior of the structure under ultimate loading. Combined with parameter sensitivity analysis, the findings provide direct guidance for practical engineering design.