The E-class power amplifier presents an ideal solution for high-frequency power supply applications, characterized by its simple topology, high operational frequency, and efficiency. This paper conducts a detailed analysis of the transfer characteristics of a four-coil wireless power transfer(WPT) system and proposes an optimal design method to achieve high transfer efficiency. Additionally, with considering the operating status of the E-class amplifier, perfect matching of input resistance is achieved by adjusting the distance between the driving coil and transmitting coil. A 2.81 MHz four-coil mid-range WPT system employing an E-class amplifier is established. At a transfer distance of 3.6 times the side length of the transfer coil, the overall transfer efficiency from the power source to the load reaches 8.5%.