Aiming at a problem of low availability of traditional photovoltaic system, taking STM32F103 whose core is CortexM3 as the system′s main chip, and taking GPS as well as4quadrant photoelectric sensor as the solar tracing device, and designed a new solar automatic tracing system. Firstly, take use of sun movement method to track roughly, then send the signal of photoelectric sensor to micro control unit after dealt with by adjust circuit, the MCU generate PWM waves to control biaxial stepper motor to adjust in the horizontal and vertical separately, so that the photovoltaic array could track the sun automatically. The experimental results show that, the control system has high tracing accuracy and operate stably and cost a litter, etc.