This article briefly introduces the development and application of servo system. With the subject of computer controlling etc, it particularly expounds the elements and flow of work in the digital servo system and how to solve the communication through the process of controlling. The research of hardware system contains the applications and disposal of direct current electromotor, shaft encoder, buffer, latch and so on, while the software comprises the programming of C language and interfacing technology between language C and the hardware. The way of controlling is PID.