Abstract: An isolated overburden grouting filling method for coal gangue underground emission reduction includes determining a grouting filling key stratum according to information of a coal face; constructing a directional borehole from an underground tunnel to the inside of the grouting filling key stratum; constructing a plurality of branch holes downward in a main hole of the directional borehole; and by establishing a grouting filling system under a mine, gangue obtained from excavation gangue of the mine and gangue sorting being made into a filling slurry by means of breaking and grinding, and the filling slurry filling fractures below the key stratum through the directional borehole. The gangue generated from a mine is directly made into a filling slurry under the mine and then fills overburden mining-induced fractures, thereby achieving harmless disposal of the gangue, effectively supporting a key stratum, and controlling stratum movement and surface subsidence.