The stabilization problem of an underactuated non-symmetric surface vessel is considered, and a new decoupling method is proposed. Based on the global diffeomorphism and time-varying coordinate transformation, the ship dynamic system can be decoupled into two linear subsystems, and the isolated global exponential stabilizing controllers are designed. Then a global ??-exponential stabilizing controller for the whole system is constructed for the ship in consideration. Finally, simulation results show the effectiveness of the proposed method.