Abstract: Underground coal mine ventilation system has a mounts of disadvantages, major factors including nonlinear regular and management difficulties. In order to ensure that the underground toxic and harmful gas does not exceed the limit, and to achieve the purpose of reducing the energy consumption of the ventilator, the PLC double closed-loop adjusting system is introduced based on the analysis of the principle and characteristics of the traditional downhole ventilation system. The wind pressure of the fan air volume can be effectively controlled according to the concentration of toxic and harmful gases; besides diluting the toxic and harmful gases, the purpose of energy saving and emission reduction can also be achieved. According to the actual tests, the response speed of the PLC double closed-loop system ventilator is significantly higher than that of the traditional fan, which can effectively reduce the phenomenon of toxic and harmful gas accumulation in the underground.