Abstract: The gas exhausting is an effective measure which must be taken when gas is over the limit set by regulation in high gassy mine.On the basis of analysis of defects of traditional exhausting methods, a closed-loop system for gas exhausting with frequency-conversion speed-adjustment technology was developed in this paper. In addition, the composition and working principle of the gas exhausting system were introduced. The system took the gas density as parameter and regulated rotational speed of local fan by PID algorithm, so as to exhaust the gas safely in working face, and ensured safe production in coal mine underground.