Abstract: In order to get the real effective drainage radius to guide the gas pre-drainage in mining-coal bed, this paper starts from the essential goal of gas extraction, based on the requirements of gas extraction up to standard, establishes the core criterion of desorption gas content in the coal seam corresponding to the daily output of the working face, and forms an effective measurement method of extraction radius by inverting the corresponding residual gas pressure and combining with the “pressure drop method”. Through the field test, according to the judgment basis and test method, the effective extraction radius of 1204 working face is 1.5 m when drainage time is 79 d, so as to guide the layout of the pre-extraction boreholes in mining-coal bed, which can meet the requirements of the extraction standard, and the gas concentration of the upper corner is 0.28% to 0.66%during the extraction, realizing the safe production of the working face, which shows that the criterion is reasonable and effective.