The artificial heart is usually powered by a wire, but the wire can cause postoperative infection, and the wire can break when used for a long time. Transcutaneous Energy Transfer (TET) technology can well solve the problem of power supply of wire. This paper proposes a high-efficiency TET system that minimizes the loss of the implanted circuit. The wide bandgap device GaN FET with preferable high-frequency performance is applied to increase power density and achieve better performance. In order to reduce heat and loss, a self-actuated synchronous rectifier circuit is designed, which has the characteristics of small volume and high working frequency.