The invention discloses a device for injecting solid powder into a high-pressure gas pipeline. The device for injecting solid powder into the high-pressure gas pipeline comprises a high-pressure gas pipeline, a hopper, a nozzle and a screw feeder. The screw feeder comprises a variable frequency motor, a gear pair, a stirrer, a toothed-rotor and a rotor outer cylinder. The variable frequency motor drives the toothed-rotor and the stirrer to rotate, solid powder in the hopper rotates along with the stirrer and is stirred, and enters a spiral space defined by the toothed-rotor and the rotor outer cylinder, and the toothed-rotor drives the solid powder to enter a discharging opening of the screw feeder. High pressure gas enters the high-pressure gas pipeline from the upstream part, and is injected through the nozzle and then carries the solid powder coming out from the discharging opening of the screw feeder, and enters the downstream part of the high-pressure gas pipeline, and a pressure balancing pipeline is communicated with the hopper and the high-pressure gas pipeline to make the pressures of the hopper and the high-pressure gas pipeline be always balanced and equal. The negative-pressure nozzle can form a negative pressure zone on the position of the discharging opening, and the solid powder is promoted to enter the high-pressure gas pipeline smoothly.