Abstract: Aiming at the difficulties that invalid drilling footage was too long and the pore-forming was difficult in the climbing borehole section of high-level directional borehole in complicated stratum of the roof in Huainan Mining Area, the directional drilling technology of strong deflection based on PDM drill with corner piece of 1.75°. The deflection ability of the PDM drill with corner piece of 1.75° was two times of the existing PDM drill with corner piece of 1.25°. It effectively shortened the length of the complicated borehole section, reduced the risk of pore-forming, improved the effective drilling footage by more than 5.4 % and successfully solved the pore-forming difficult of lower stratum. With this technology, 14 high-level directional boreholes in the roof were carried out successfully. It had made an important contribution to the realization of “replacing the roadway with boreholes” in Huainan and similar geological conditions mining areas.