In this study, a dual-frequency power amplifier (PA) is proposed to apply for the wireless power and data transfer, and the design model is analyzed mathematically in detail. A single dual-frequency PA can be applied for both modes by modifying the traditional class-E PA with an additional shunt impedance which has dual poles. The proposed power amplifier is designed to transfer data at 1 MHz and transfer power at 13.56 MHz. Furthermore, the mathematical model of the proposed power amplifier and its design equations are clearly calculated. The PA is demonstrated to be high efficient at both 1 MHz and 13.56 MHz in simulation. The output power and power added efficiency at 1 MHz is 193 mW and 90.53%, respectively. At 13.56 MHz, the output power and power added efficiency is 179 mW and 90.93%, respectively.