In the harsh operating environment of deep sea, the underwater autonomous vehicle is affected by the seawater disturbance, and the magnetic coupling structure may have certain offset, causing the transmission power and transfer efficiency of the system to decrease. In this paper, an equivalent mathematical model of DD orthogonal wireless power transfer system is established to analyze the output characteristics of the system; the influence of the input voltage amplitude and phase difference of the resonant network on the transmission power and transfer efficiency is studied; an efficiency optimization control strategy is proposed to optimize the system efficiency and control the output power by controlling the ratio of the input voltage amplitude of the resonant network; Finally, it is experimentally verified that after using this control strategy, the efficiency of the magnetic coupling structure is improved by 1.7% under the case of 100mm x-axis offset, and the system can still maintain stable and efficient power transfer under the situation that the coupling coefficient changes in a wide range.