A paint ball gun includes a frame defining a frame bore therein and a valve located below the frame. The valve communicates with a first path which communicates with the barrel. A bolt and a strike rod are received in the frame bore. The valve guides pressurized air to the rear end of the strike rod to move the strike rod to push the bolt which has a central passage. When shooting, the central passage opened and the pressurized air flows through the central passage to eject paint balls.