Aiming at the control requirements of maximum efficiency and constant voltage output of dual-channel wireless power transfer ( WPT) system under load and mutual inductance variation, a maximum efficiency control method based on equivalent load tracking is proposed in this paper. First, a rotary-coupled WPT system with a double-layer quadrature DD ( DQDD) coil as the transmitting mechanism and a crossed dipole (CD) coil as the receiving mechanism is constructed. Subsequently, the parameter configurations of the LCC-S network in dual-channel WPT system are carried out considering the cross-coupling and the internal resistance of the coil, and the expressions for the transmission power and efficiency of the system are derived. Then, a composite control method is introduced to regulate the output voltage of the system by using a Buck circuit at the DC input, while a Buck-Boost circuit is applied at the output load to achieve impedance matching. Finally, simulations and experiments validate the accuracy of the derived expressions for loop current, input / output power, and efficiency, as well as the feasibility of the resonance component configuration when accounting for coupling circulating currents. The results demonstrate the accuracy of the mutual inductance identification results, showing that the system can realize the maximum efficiency tracking and constant voltage output, with the transmission efficiency maintained above 90% .