Abstract: In order to solve the problem of hole-forming difficulty of the climbing segment of high-level large-diameter directional long borehole at seam roof in Guqiao coal mine, grouting reinforcement borehole, through-hole with special drilling tool combination, reaming with differential bottom hole assembly were tested. The paper briefly introduced the technical principle, construction process and field tests of three kinds of drilling techniques, the results show that reaming with large diameter differential drill assembly could solve the problem effectively, and 14 boreholes deeper than 500 m were successfully drilled by using this technology. The matters needing attention when using large diameter differential reaming technique were pointed out, a set of techniques and methods with popularization value has been formed.