The invention discloses a coal mine underground hydraulic fracturing drill hole sealing device and a method. The coal mine underground hydraulic fracturing drill hole sealing device comprises a fracturing pipe, a grouting pipe and a slurry return pipe, wherein the frontmost end of the fracturing pipe is positioned at the hole bottom position of a fracturing drill hole; the grouting pipe is used for grouting into the fracturing drill hole; the frontmost end of the slurry return pipe is positioned in the position of a coal seam bottom plate and is used for slurry return and secondary grouting; a centering element used for ensuring the fracturing pipe to be positioned in the middle position of the drill hole is arranged on the fracturing pipe; the mortar grouting quantity and the position away from the coal seam can be mastered; a hole sealing layer is ensured to be positioned at the coal seam section; the fracturing drill hole abandoning due to blockage of the tail end of the fracturing pipe by cement is prevented; meanwhile, the problem that the fracturing pipe is tightly attached to the hole wall after being put down, so that the hole sealing intensity cannot be ensured can be solved; and the water leakage avoidance in the hydraulic fracturing process after the hole sealing of the fracturing drill hole can be ensured