A device and a method for adjustable quantitative injection of high-pressure gas are provided, wherein the gas may have a pressure of 5 MPa or more than 5 MPa. The gas may be directly communicated with a gas tank in the mechanism or an external gas source, flows through corresponding valves, and is charged into a predetermined or adjustable reservoir. Alternatively, the valve may be time-controllable, and does not need the reservoir. The gas is ejected through a nozzle selected based on depth or range of injection, wherein a one-way valve is disposed between the nozzle and the body to prevent contamination due to backflow. The manipulator can exert an appropriate force onto a target portion of a human for gas injection, and when the injection is done, a biasing member can automatically return the mechanism to its original state, ready for the next injection.
