Abstract: In order to ensure main ventilator run safely, reliably and economically, the paper proposed a design scheme of automatic monitoring and control system of mine main ventilator based on S7-300 PLC. It gave structure of the system and detailedlly introduced structure of hardware and software of PLC, implementation of detection for analog and using intelligent PID regulator XMA5000 to control negative pressure and flow of ventilator in the system. The actual application showed that the system can realize three control modes of in site control, integrated control and remote control, and improves automation degree and operation reliability of main ventilator.