. A paintball gun comprising a frame coupled with a pressurized air flask; a barrel being provided to the frame; a paintball drop hole being disposed at a top end of the barrel, the barrel being connected to an air storage chamber; a port and a keyhole being provided between the air storage chamber and the barrel; the air storage chamber connecting through the pressurized air flask; and a trigger being disposed to the frame, and characterized in that:
a T-valve being provided inside the frame to control the passage of low-pressure air;
a sticker being disposed in the barrel; an opening being provided to a front edge of the spool; a piston being inserted into the opening; a spring being disposed between the piston and the spool; both the spool and the piston being respective provided with through holes connecting through their outer edges; and a through channel being provided at a rear end of the spool; and
a low-pressure regulator being provided inside the air storage chamber, the low-pressure regulator comprising a block therein;
thereby, the T-valve controlling admission for the low-pressure air to enter into the through channel once the trigger being pulled to push the piston forward and to advance a paint ball; the pressurized air leaving the air storage chamber to pass in sequence through the port, the opening of the spool, the through hole of the spool, the through hole of the piston to shoot the paintball; the low-pressure regulator being turned to plug the port for preventing the pressurized air from entering into the barrel through the air storage chamber to avoid hurting people by accidentally pulling the trigger.