Influenced by the operating environment and working time, the radio frequency impedance load is constantly changing, which may affect the output power and the efficiency of the RF source. Therefore, a matching network is needed between the RF source and the load, which can track the changes of load impedance dynamically and make corresponding adjustments to matching network elements, thus to maximize the output power of the radio frequency source. According to the changing characteristics of the radio frequency source load, model matching network is chosen in this paper. The control law of the adjustable elements of the matching network is controlled by the change rule of Smith chart. The current and voltage signals are detected respectively by Roche coil and the capacitive divider, which are then input to AD8302 amplitude/phase detection circuit for obtaining signal amplitude ratio and phase difference. After analog-to-digital conversion, the signals are input to STM32. According to the characteristics of impedance and admittance in Smith chart, PID algorithm is used to control the stepper motor and the steering angle, thus a new closed-loop control system is realized. The experiment and simulation results show that the circuit can be quickly matched in 5 s, and the error is controlled within 3 degrees.