The stability of the multi-floating body crude oil transfer system, which contains three vessels: the Crude Transfer Vessel (CTV), the tanker and the tugboat, during the offloading operation in the South China sea is analyzed. The real complex environmental loads (including wind load, current load and wave load) of the multi-floating body system are considered with the respect to the vessels positioning and towing modes, the possible positions of the multi-floating body system to maintain quasi-static state equilibrium under different environmental conditions during the offloading operation are studied, and the minimum force required by the CTV thruster to maintain quasi-static state equilibrium is obtained. The results show that the angle between the three ships must be within certain range for the specific wind, current and wave load directions to maintain the balance of the multi-floating body system.