In order to meet the requirements of vehicle photoelectric theodolite on the control precision, stability, weight and volume of the servo control system, relevant research was firstly carried out on the main power supply of the servo control system. As the energy supply unit of the servo control system, the stability of the main power supply determined the stability of the servo control system. Then the tracking precision and tracking frequency of the servo control system were affected. In this paper, the design requirements of the power supply, the main circuit, the maximum pulse width limiting circuit, PWM control circuit, voltage and current detection circuit and voltage feedback control circuit were described. At the same time, the power supply was designed according to this method, and the test results were obtained: the power output is 48 V DC; the output power is 2 400 W; the peak-to-peak value is 310 mV; the weight is 13.8 kg; the volume is 350 mm×200 mm×110 mm.