Abstract: An air gun chamber structure is composed of a valve seat, a valve, a valve cap screw, a nozzle, a nozzle seat, and related fittings. The valve seat is divided into two parts by a baffle, the valve is limited to a rear side of the valve seat by the valve cap screw, and the nozzle is limited to a front side of the valve seat by the nozzle seat. A pillar at a front end of the valve is transfixed into a vent-hole at a center of the baffle and is inserted into an opening at a rear end of the nozzle, an outer wall of the valve is provided with an indent section, at a position where the valve passes through the vent-hole, and a proper notch part is located at a portion of rear end of the valve which is inserted into an air hole at a center of the valve cap screw. In normal times, the rear end of valve is kept at being tightly connected into the air hole. Accordingly, after the valve is subjected to an impact, a time difference will be formed that a bullet will be ejected first prior to pulling back a slide.