The energy efficiency of the magnetically coupled wireless energy transmission system is greatly affected by the distance between the primary and secondary coils. In the over-coupled state, the energy efficiency will decrease as the transmission distance decreases due to the frequency splitting of the system. In this paper, the actual eigenstate working conditions of the system are obtained through the eigenmode theory so that the system can ensure maximum energy efficiency in the over-coupling region and the similating betewwn the actual eigenstate and the real eigenstate is compared from the perspective of the zero phase angle point. Thus, frequency tracking is used to make the system maintain constant power and constant efficiency output in the over coupling region. Finally, the correctness of the calculation results in this paper is verified by simulation.