Gas drainage drilling effective drainage radius of the mine layout is an important basis for reasonable drainage drilling spacing, the gas content of descent was used to inspect at 21212 railroad in Dongpang Mine, the effective pumping coal seam No. 2 Mining radius definition standard was determined. The results showed that when a sac bag type two plugs and one injection were used in the φ113 mm bedding hole of No. 2 coal seam and the extraction negative pressure was 16-22 kPa, the effective extraction radius of 10 d was 1.0 m, and the effective extraction time was 30 d as effective drainage radius of 3.5 m, which provided a basis for gas drainage.