The invention discloses a downhole rapid slotting directional hydraulic fracturing system and method based on drilling machine power. The directional hydraulic fracturing system comprises a water injection pump, and a high pressure rubber hose is arranged on the water injection pump to communicate with a drilling machine. A special sealing drill pipe for hydraulic fracturing is installed on the drilling machine, and the front section of the drill pipe is connected with directional hole packers in a threaded mode. Sealing rings are arranged at the threaded connected positions. The downhole rapid slotting directional hydraulic fracturing method comprises the main implementation steps of hole drilling, slotting, hole sealing and fracturing, specifically, a drilling and cutting integrated toolis installed at the front end of the drill pipe firstly, and after the hole drilling is completed, hydraulic slotting and anti-reflection pressure relief are performed without replacing a drill bit;after the slotting is completed, the drill bit is withdrawn, and the directional hole packers are installed and pushed to the predetermined positions for high-efficiency hole sealing; after the hole sealing is completed, high-pressure water injection fracturing is carried out, and high-pressure permeation is mainly used for increasing the fracture density and range, so as to improve the water injection effect of a high ground pressure and low porosity coal seam, effectively prevent and control rock burst, reduce dust concentration, prevent and control gas and prevent and control fires and other disasters.