Abstract: In order to improve the borehole grouting reinforcement effect of seam floor in underground mine, the paper provided a borehole floor grouting reinforce ment technical method with a drilling measuring and directional drilling technology. A systematic study was conducted on the casing drilling, rotary deflection drilling, dir ectional deflection drilling and through hole drilling technology and matched drilling tools. A drilling technical procedure was designed. The site trial results in Zhaogu N 0.1 Mine showed that the directional drilled borehole could realize the advance treatment of the seam floor, the grouting quantity of a single borehole would be increas ed by a large margin and the seam floor reinforcement effect was obvious.