The South China Sea is under harsh conditions, and after many years of service in the South China Sea, few module stools of FPSO have cracked due to construction process problems. In order to avoid construction risks, taking a deep-water FPSO in the South China Sea as the research object, the box-type form of the commonly used FPSO module stool in the South China Sea was improved and optimized, and the box-type module stool and the improved Fengzi module stool and the cross belt skirt stool were evaluated by using the finite element method, and the strength analysis, deformation analysis and fatigue analysis of different support forms were carried out, and the construction technique of different stool was comprehensively compared. Combined with engineering practice and finite element calculation, the recommended module stool was given. The results show that the structural strength and fatigue of the optimized cross belt skirt stool meet the requirements, and it also has the characteristics of easy processing and assembly, and the scheme of cross belt skirt stool is selected.