Servo motor based on PLC control was introduced in the steel tape automatic measurement system. Electric control system design of the steel tape automatic measuring system based on PLC was expounded. The system hardware and software design were discussed, including the electrical circuit design, software programming, PC communication, PLC controlling servo motor location and the work driving. The results show that this system can be used to realize quick and accurate control to the measurement. It has characteristics of high degree of automation, good reliability and easy operation.