Aimed at the problem that the South China Sea is under harsh conditions, after years of service, cracks are found on the module stools of Floating Production Storage and Offloading (FPSO) due to construction technology troubles, taken a deep-water FPSO in the South China Sea as the research object, the box-type form of the commonly used FPSO module stool is improved and optimized. The box-type module stool, the improved Fengzi module stool and the cross belt skirt stool are evaluated by the finite element method. The strength analysis, deformation analysis and fatigue analysis of different stool forms are carried out. The construction technologies of different stools are comprehensively compared. Combined with engineering practice and finite element calculation, the recommended module stool is given. The results show that the optimized cross belt skirt stool is of better performance in strength and fatigue, it also has the characteristics of easy processing and assembly, and the scheme of cross belt skirt stool is selected.