Abstract: Based on wave radiation/diffraction theory，the motion responses between two ships in the wave were considered by hydrodynamic analysis software AQWA.The influences of the Floating Production Storage and Offloading(FPSO)on added mass and radiation damping of the barge were discussed，and the drift forces and motion responses of barge were analyzed.The results show that when the distance between two ships is 5 m ，the barge S added mass for the case is twice as much as the case when distance is 10 m ，the added mass and damping will gradually increase when such distance reduces.The lower the speed of the barge，the smaller its drift force，and the more intense rolling and yawing motion would occur when distance is 30 m.