The internal turret mooring system is a critical system for FPSO, and safety of hull reinforcement structure is critical to the operation of the FPSO. Through the introduction of the current mainstream internal turret FPSO interface form and design concept, the different concepts of load transfer of single-point mooring systems of different internal turrets are analyzed and compared. By comparing and analyzing the typical internal turret FPSO mooring system reinforcement design, the key points that should be paid attention to in the reinforcement structure design of different internal turret mooring systems are given. Strength and fatigue design of different classification societies are compared. The basic process and focus of structural strength and fatigue analysis are expounded. The results show that the interface form, load form and reinforcement structure form of different internal turret systems are different. Special attention should be paid to the effect of torque in the evaluation of structural strength. The influence of wave frequency load and low frequency load should be considered in fatigue evaluation of reinforced structures.