In recent years, as servo motor technology, power electronic technology and computer control technology development makes the servo control system toward control circuit operation.this digital and the modular direction. And MCU use technology has also gradually mature, in various fields can be widely used. This paper introduces the AT89C51 as control core dc servo control system, and the working principle of hardware design and software design from two aspects of dc servo control system is introduced the idea and method of design, it includes the main program design, given a program design, modify the program design, start programs design and T0 interruption program design and PWM system driver circuit design and its relevant protection circuits. Through quantitative and feedback to the amount of compare and PID control procedures, the output of certain voltage, to implement the accurate tracking system to position In recent years, as servo motor technology, power electronic technology and computer control technology development makes the servo control system toward control circuit operation.this digital and the modular direction. And MCU use technology has also gradually mature, in various fields can be widely used. This paper introduces the AT89C51 as control core dc servo control system, and the working principle of hardware design and software design from two aspects of dc servo control system is introduced the idea and method of design, it includes the main program design, given a program design, modify the program design, start programs design and T0 interruption program design and PWM system driver circuit design and its relevant protection circuits. Through quantitative and feedback to the amount of compare and PID control procedures, the output of certain voltage, to implement the accurate tracking system to position