Magnetically coupled wireless energy transmission technology is non-contact and safe. Aiming at the charging characteristics of lithium batteries, this paper proposes a switching magnetic coupling wireless charging system with constant voltage or constant current output in a variable structure. This system does not require complex communication structure and control logic, through the three switch structures, you can realize the system output constant current / voltage and switching, with simple control, switching process continuity, the advantages of simple design. The overall structure and working principle of the S-S/LCC compensated Wireless Power Transfer (WPT) system are firstly given, then the constant current and constant voltage output characteristics of the system are analyzed respectively, the design method is given, and finally the feasibility of the system is verified by simulation.