Abstract: Taking ShaQu Coal Mine as the research background, it built the model based on the theory of elliptical parabolic zone and "three vertical belts" which formed as working face overburden collapsed after mining, then it studied the gas drainage technology of large diameter high level boreholes. Through analyzing the movement and distribution law of pressure relief gas in coal seams, it showed that the best drainage effect was obtained by putting terminal borehole into the overlay area of upper half fracture zone and elliptical parabolic zone, and the calculation formula of the borehole elevation angle and the range of azimuth value were given. The extraction data of the No.24207 working face showed that, the average extraction concentration of drilling field was about 42%, and its average extraction pure quantity could reached 11.6 m³/min.