Abstract: A gas decompression magazine of a toy gun comprising a bullet guiding slot and a container installed in parallel inside the magazine, a decompression valve is inside the container and subdivides the container into a gas bottle chamber and a decompression chamber, a control valve is on the top of the magazine, a gas bottle is installed inside the gas bottle chamber and connects to the decompression valve; the major character is: a plunger and a compression spring are installed in series inside the valve body of the decompression valve, then are threaded sealed by a cover on the top of the valve body; while application, users can adjust the depth of the cover inside the valve body to change the distance between the bottom of the cover and the top of the plunger, the decompression strength of the compression spring in between changes, the shooting gas pressure after adjustment can meet the safety requirement.