Abstract: Gas concentration is one of the main indicators to measure the quality of gas drainage, and the leakage in boreholes sealing section is the main reason to reduce the gas concentration. Therefore, in order to analyze the distribution characteristics of the air leakage field in the surrounding of boreholes and to guide the determination of the air leakage location.The air leakage field in the surrounding rock of boreholes was simulated and analyzed by using Fluent software, and the distribution and strength characteristics of the air leakage in surrounding rock under different sealing conditions were obtained.And a fixed point measuring device of methane concentration in the drainage borehole was developed, witch can provide a reliable basis for increasing gas concentration in borehole drainage.The results show that the sealing depth of boreholes and coal wall cracks have obvious control effect on gas leakage in the sealing section of boreholes. And the leakage of gas extraction borehole in the return air channel of GaoHe Energy W4301 is mainly caused by the insufficient sealing depth and length of the borehole and the small spacing between the boreholes.By increasing the sealing depth and length of the borehole, the average concentration of gas extraction in a single hole can be increased by 3-5 times.The results of the study are important for quickly analyzing the characteristics of the holes in the hole, and making the appropriate increase in the production of the gas.