Abstract: In order to accurately measure the effective influence radius of in- seam borehole under the available gas pre- drainage condition of XinDan Mine, under the different space of the boreholes, the gas drainage flow method was applied to determine the effective influence radius of the gas drainage borehole according to the variation of the gas flow. The results showed that the effective influence radius of in- seam borehole determined with the gas drainage flow method was 1. 2 m and coul d be ftted with the previous measured results. Thus the effective influence radius of in- seam borehole determined with the gas drainage flow method was proved to pro vide references to the layout of the site boreholes space.