In order to reasonably determine sealing distance of gas drainage and avoid short circuit flow, Shaqu mine was taken as the research object. Drilling in bottom pumping roadway was designed through overlying No.3, No.4 and No.5 coal seams, which set different sealing distances and measured gas drainage concentration. The result showed that short circuit flow occurred when sealing distance was 3m, and it didn’t show up in 5m and 15m sealing distance. It was clear that development range of roadway fracture zone was from 3m to 5m.