Abstract: The problem of underway replenishment control for vessels cruising in formation is investigated, which is treated as a synchronizing path tracking control problem of the replenishment ship and the group of vessels cruising in formation. Based on Lyapunov stability theory, a nonlinear adaptive PD (proportional-derivative) control method is presented for path tracking control of the replenishment ships which can reject the influence of environmental disturbances induced by the wave, the wind and the ocean-current. Based on a consensus algorithm and graph theory, a trajectory controller is designed for the replenishment ship to synchronize with the ship formation in the presence of unreliable communication. The simulation results prove the correctness and effectiveness of the proposed control method.