Abstract: In a high power microwave system, the precise control of the microwave beam is achieved by controlling the position of the multichannel phase shifter. In the design of servo control system, in order to reduce the interference and damage of the strong electromagnetic field to the servo system, the control system conceptual design, phase shifter design, position sensor design, position loop design, circuit board design, chassis design, transmission cable and other aspects are strictly executed and handled. During the design process, field experiments were carried out for the verification and selection of the key components. Consequently, the high-power microwave system is stable and reliable, and the beam control achieves the expected precision (0.1 mm) in a test of continuous radiation on the target.