Abstract: In order to effectively control hole-spraying in hydraulic slotting drilling, its igniting mechanism was analyzed systematically, after which, two kinds of slotting modes-"strong water and sharp cutting" and "fine water and blunt cutting" were put forward. Through FLAC^3D numerical simulation and engineering practice, the effect of different kinds of slotting modes on hole-spraying was studied particularly. Results indicate that the coal is severely damaged by means of "strong water and sharp cutting"slotting, as the mechanical parameters and displacement change significantly and lots of coal and gas spurt during industrial test. Finally, outburst elimination and controllable hole-spraying are both taken into consideration, 15 MPa, 160 r/min are regarded as the optimal slotting water pressure and drill rotation speed.