Ship-shaped floating production units (FPU) may appear the phenomenon of sagging and hogging during service, and the deformation of main deck will affect the module located on its upper part. The braced frame is usually set between the FPU hull and the upper module. The traditional design method takes the surface deformation of the hull main deck as the displacement boundary condition of the upper module, without considering the influence of the braced frame, resulting in conservative design of the upper module structure. In this study, the finite element analysis method is introduced to simulate the braced frame on a full scale and the influence of the braced frame on the relationship between the deformation of the main deck and the relative displacement of the fixed end of the upper module is analyzed. The results show that the actual longitudinal deformation value of the supporting frame is much smaller than that of the hull main deck. Based on the finite element analysis (FEA), a correction method is proposed to simulate the displacement load of the fixed end of the upper module. This method can improve the precision of the upper module structure design, reduce the amount of steel and optimize the module space.