Abstract: In order to solve the problems existing in contact power supply, such as leakage, wear and tear, poor power transmission, and in the processing of ultrasonic power supply, such as resonant frequency drift, slow tracking speed and unstable output power, a contactless powered ultrasonic power supply with adjustable frequency and power is designed by using STM32 single chip microcomputer as the main control system in this paper. According to the phase difference and effective value signals of voltage and current collected by the sampling feedback circuit, the frequency is tracked by the combination of phase locked loop and fuzzy proportional integral (PI) control, and the output power is controlled by the traditional PI control method. The simulation model of power supply is built in Matlab, and the sudden change of load parameters in the process of machining is simulated by using additional resistance, additional inductance and additional capacitance. The power supply models with frequency regulation and power control subsystems and without subsystems are simulated respectively. The simulation results show that the output power of the power supply is stable at 248 W. When the load parameters change, the resonant frequency of the power supply drifts, and then, by adjusting the frequency automatic tracking subsystem, the power supply will return to the resonant state after 0.01 s. The control algorithm realizes fast frequency tracking and power control.