Using wireless charging method to charge high-temperature superconducting (HTS) magnet is a way to solve the existing problem of high leakage heat introduced by charging through current leads. However, the available studies on charging HTS magnets using wireless charging methods rarely involves the role of Dewar on the charging process. Nowadays, most HTS magnet use metal Dewar because of the high requirements of Dewar for gas tightness and mechanical strength. How to charge the HTS magnets wirelessly through metal walls of the Dewar is an issue that needs to be addressed. In response to the above concerns, taking into account the role of the metal Dewar, a low-frequency wireless charging system with an isolation transformer as the core is proposed in this paper. Theoretical model of the proposed wireless charging system is developed, and the prototype is fabricated based on the theoretical model. Both theoretical and experimental methods were used to study the operational characteristics of the prototype, and the results obtained proved the validity of the theoretical model in this paper. Experimental results show that the proposed wireless charging system can charge an 8.5 mH HTS magnet with a current of 48.58 A over a 6 cm transmission distance, where the 6 cm gap includes a 1.6mm thick metal wall. Results obtained in this paper can provide a new idea for the research work on charging HTS magnets wirelessly through metal Dewar.