The fatigue characteristics of the floating platform with shell plate structure under the environment of the South China Sea are serious, and the fatigue design of the hull structure of the semi-submersible production and storage platform under the requirement of 30 years undocking inspection and repair requirement faces great challenges. The structural fatigue analysis of the platform is carried out. The fatigue hot areas of the hull structure are given based on the platform characteristics. The fatigue requirements and fatigue improvement methods of different rules are analyzed. The fatigue improvement methods suitable for the project are studied. Different design methods are compared, and the construction plan to improve the fatigue life of bracket toe, fillet and butt weld is presented. The in-place inspection plan for the platform is developed. Through high-quality fabrication and detection, the hull construction quality is ensured. The fatigue design results are successfully implemented in the construction of the project, which provides an important guarantee for the in-place operation safety of the platform.