Abstract: In order to solve the problem of gas transfinite at upper corner,which gas in goaf was extrusion by hanging arch at trigonum of fully mechanized coal mining face collapsed suddenly of Hecaogou coal mine,and then roof water fracturing method was applied at 50115 ventilation roadway,the experiment was applied in filed,which length was about 50m,about four times periodical pressure appeared at working face roof within water fracturing section,according the whole observation of face end collapse,and the face end roof collapse timely and fully at testing section,and gas transfinite problem was solved successfully.