Coal mine gas drainage remains an important measure to reduce gas emission rate and prevent gas explosion and coal and gas outburst disaster. Sealing quality, diameter, spacing, depth, permeability of coal seam directly influences the gas drainage effect. Reasonable arrangement of hole spacing enables to avoid gas drainage blind area and reduce human and material resources. As an important parameter in measuring drilling spaces, extracting radius settlement avoids blindness in the design and construction of borehole spacing. The testing of the extraction radius of No. 9 coal seam in 28210 roadway of Dongqu Mine, pressure drop method in measurement of gas extraction radius of borehole along the horizon was effective and feasible, extracting radius means a lot in improving the extraction effect, arranging construction schedule reasonably and preventing coal and gas outburst.