In order to improve the stability and reliability of the gas drainage monitoring system, reduce and eliminate the hidden danger of gas overrun safety accidents caused by the monitoring system failure. We designed a gas drainage monitoring system based on redundant control technology. First of all, we designed the overall architecture of the monitoring system. Siemens S7-1500R series programmable logic controller (PLC) was used as the core control unit, redundant design was carried out for CPU and DC24V power supply, and the PLC control cabinet was designed according to the on-site requirements. In the design, smart sensors and digital signal transmission are used to improve the anti-interference ability of the system. Secondly, we designed RS485 communication program and PID control program in portal software to realize data acquisition of smart sensors and constant pressure control of gas drainage system. Finally, we use WinCC configuration software to design the human-machine interface (HMI), which realizes the online monitoring and remote control of the gas drainage system. The application shows that the switching time from the primary CPU to the backup CPU automatically due to failure is about 300 ms. In addition, when any CPU, profinet cable or power supply fails, the system can still work normally, effectively improving the stability and reliability of the gas drainage monitoring system, and achieving the goal of monitoring the gas drainage system efficiently.