Abstract: For the problem of large gas emission amount from adjacent coal seam and frequent gas overrun at upper corner of 8204 fully mechanized working face of Mabu Coal Mine, the characteristics of mine gas inflow at 8204 working face was analyzed，thereby, the gas extraction technology for long & large diameter roof boreholes was proposed. What's more, the characteristics of strata movement and failure development above goof at working face were analyzed by FLAC^3D numerical simulation, based on this, the drainage parameters were designed. The field application result shows that the gas extraction technology for long & large diameter boreholes can effectively intercept gas from adjacent coal seam and save the problem of gas overrun at upper corner due to gas emission, and guarantee the safety high production and efficiency of working face．