Abstract: In the process of high-level directional drilling instead of high-level drainage roadway to control upper corner gas，the hole diameter is one of the main factors affecting the implementation effect of the process. In order to improve the hole-forming efficiency of large-diameter high-level directional drill⁃ ing，through the comprehensive analysis of the factors of low construction efficiency caused by the existing high-level directional drilling multiple hole-forming process，drilling tool assembly，hole accident and so on，the hole-forming process of large-diameter high-level directional drilling is improved from three as⁃ pects of drilling rig selection，drilling tool matching and construction technology，so as to realize the onetime hole-forming of large-diameter high-level directional drilling. Through the test in Wangpo Coal Mine，the average construction efficiency of 200 mm hole diameter and 501 m final hole depth is 90 m/d， and the hole forming efficiency is increased by 76.5%. The new technology has the characteristics of simple process，high construction efficiency and strong accident prevention and treatment ability.

Key words: high-level directional borehole, drilling process, the efficiency of hole-forming, drilling liquid