Abstract: Based on the gas flow method, the corresponding relationship between drilling gas flow and extraction time of 4^-2 coal seam in Qinggangping coal mine under different drilling spacing is investigated, aiming at the problem that blind arrangement of drilling spacing causes prominent safety hidden dangers in mining and gas control cost surges.The results show that:under different drilling spacing (2 m, 3 m, 4 m and 5 m), there is a negative exponential attenuation relationship between the extraction flow and time, and a negative exponential increasing relationship between the total amount of extraction and time.The smaller the spacing is, the smaller the initial extraction flow is.Under different drilling spacing, the gas extraction rate has an extreme value.The smaller is the spacing, the greater is the increase of the limit extraction rate.When the spacing is 2 m, the maximum value reaches 79%.There is a dynamic coupling relationship between the gas extraction radius and the pre-pumping period.In the case of comprehensive consideration of the reasonable pre-pumping period and the cost of gas treatment, the effective extraction radius under the current extraction conditions is determined scientifically, which provides a theoretical basis for the gas extraction design of the 4^-2 coal seam mining face in Qinggangping coal mine.