To optimize the existing automatic control system of paper machine and improve the quality of paper, a mechanical automatic control system of paper machine based on programmable logic controller (PLC) was researched and designed. First, the development status of the paper machine control system was introduced. Then, according to the paper making process, the key points and difficulties of the paper machine control system design was summarized. In view of constant tension control, load distribution control and speed chain synchronization control, the control mechanism and control strategy were analysed respectively. Then, the auto disturbance rejection control (ADRC) algorithm was introduced, and the simulation model of the speed chain synchronization control system was built in the toolbox of MATLAB. Moreover, the ADRC algorithm was applied to the simulation model of the speed chain synchronization control. The simulation results showed that the speed chain control system based on ADRC had better performance than traditional PID control in steady state performance, dynamic performance and disturbance rejection performance. It is concluded that the speed chain synchronization control system with active disturbance rejection controller is better than the ordinary PI controller in regulating time, overshoot and disturbance resistance.