Abstract: Most parts of the No.9 coal seam in Zhangba Well of Liliu coking coal group,had been destroyed by small coal mines indiscriminately mining,which caused very serious air leakage in the face and carried large amounts of harmful gases to the face,it was a serious threat to the safety of workers.By analyzing air leakage characteristics in the goaf,the measures of hazardous gas detection technology in old mining area and face pressure equalizing technical had been proposed.Supplemented by timely and reliable management of hazardous gas detection means,this effectively solves the issue of harmful gases overrun in the working face.