The assembly support is an important supporting component in the whole construction process of the upper module of FPSO. The assembly support is set between the lower flange of the beams and site. It bears various loads in the construction and commissioning process, and it’s successful design plays an extremely critical role in the safety of the construction for topside module. Based on the detail design date of a large FPSO construction project, use SACS software to calculate the expected reaction force at each axis position of the topside modules of FPSO, and use it as a reference value to check whether the load-bearing capacity of the final assembly support can meet the requirements during construction. Then ANSYS software is used for modeling calculation and analysis, and the maximum bearing capacity of different types of assembly support is obtained within the allowable range of stress, and the expected support and reaction force are compared and analyzed. The result shows that the bearing capacity of the two different types of assembly support can meet the requirements of the construction stage, and the ground pressure is also with the allowable range of the foundation bearing capacity.