Abstract: In order to accurately determine the effective drainage radius of drill hole along coal seam,according to the Darcy’s law and the law of conservation of mass as well as the theory of gas flow and occurrence,the gas flow equation of gas extraction drill hole along coal seam was established to study the flow field of coal seam gas around the drilling.Taking Qinxin mine as an example,the gas flow equation was simulated under different drainage negative-pressure and drainage time by using COMSOL software,and the reasonable drainage negative-pressure,drainage time and the effective drainage radius were determined.