Objectives  In view of the operational sea conditions of FPSO (Floating Production Storage and Offloading) ships in the South China Sea, this paper studies the optimization of the multi-point mooring system and side-by-side coupling system of FPSO ships and shuttle tankers.

  Methods  ANSYS-AQWA software and the potential flow theory is used to conduct time-domain analysis, optimize the mooring line segments and proportions, as well as the position of the fairlead; and Fluent software is used to analyze the influence of the change of draft on the wind and current load when the two ships are abreast.

  Results  The results show that a top section of 200 m of steel cable and a bottom section of 316 m of ship chain is the most suitable FPSO multi-point mooring structure for a water depth of 200 m. Maintaining tension on the side-by-side mooring line or increasing its weight can reduce the movement range of the shuttle tanker. After the position of the fairlead is moved to midship, the forces on the fender and mooring line become more uniform. When the weight of the alongside cable is 135 kg/m, the maximum and average values of the fender and alongside cable forces can be minimized.

  Conclusions  The results of this study have reference value for better understanding the influence of mooring parameters on mooring line tension and its influence on the movement of the ship, and can be used to optimize the design of mooring schemes.