Abstract: A switch function is presented to smooth control instructions and avoid system vibration during switch operating underwater vehicles with rudders and thrusters.And a modified S-plane controller (MSC) is proposed by analyzing underwater vehicle's dynamics and taking static force and coupling effects between the longitude velocity and other dimensions into account.Besides the advantages of S controller such as simple structure,MSC can solve the problem of the motion control of underwater vehicle at high speed which is difficult to control with the S-plane controller.The stability of MSC is analyzed with Lyapunov function.Finally,MSC is applied to the motion control of an autonomous underwater vehicle controlled by rudders and thrusters.The feasibility of MSC is demonstrated by the results of velocity control,yaw control and depth control tests.