1.School of Resources Safety Engineering,China University of Mining and Technology (Beijing),Beijing ,China;2.School of Mechanics and Civil Engineering，China University of Mining and Technology(Beijing)，Beijing ，China;3.Chongqing Research Institute Co.,Ltd.，China Coal Technology and Engineering Group,Chongqing ,China

In order to solve the safety hazards of the ventilation in the gob of the multi-entry ventilation system and the gas overrun of the U-type ventilation system,based on the current situation of ventilation systems and gas drainage of the large mining height working faceitsgas control model was established.The gas migration characteristics of large mining height working face under different ventilation systemswere researched by the drainage-seepage model and numerical simulation,and the layout of directional drilling and penetrating drilling under U-shaped ventilation system were optimized and were verified by gas drainage.The results show that the guiding system of large-diameter drilling borehole changes the flow field of large mining height working face and gob,and forms a low gas concentration zone in the lower part of the gob; under U-type ventilation system,gas drainage flow will be improved greatly by using roof large diameter directional boreholes of ø153 mm in the middle and high fractured zone and large diameter pierced boreholes of ø250 mm with 5 m interval,which greatly avoids gas overrun.