Abstract: A hydraulic accumulator-based controllable pressure injection device includes a pressure storage system, a pressure maintaining system, a sealing system, and an injection system. The pressure storage system includes a pressure cylinder front half portion, an annular piston and a middle connecting body. The pressure maintaining system includes an accumulator, a pressure cylinder rear half portion and a rear end cover. The sealing system includes a hydraulic propulsion cylinder, a propulsion piston, a front end cover, a sealing tube, a thickened end portion, and an expansion rubber tube. The injection system includes a hydraulic valve body and an injection gun tube. The hydraulic accumulator-based controllable pressure injection device quickly applies pressure to the bottom of a borehole in a hydraulic manner, so that rock experiences tensile failure, and the hard rock excavation efficiency is improved.