Abstract: A control device for hitting nails of a pneumatic nail gun includes a control valve. The control valve is arranged in a main air flow passage between a trigger of the nail gun and the main air valve. The control valve has valve cover to open or close the main air flow passage. A valve bolt is slidably disposed in the valve cover. The valve bolt can be driven by the high pressure air to move down. A safety slide pole is slidably disposed in a gun body for blocking or releasing the valve bolt to move down. Therefore, a position of the safety slide pole can reflect a height of a work part which to be nailed. The valve bolt can detect the height reflected by the safety slide pole to guide in the high pressure air from the main air flow passage to hit nails. Thus, the controlling stability is enhanced. The components are also simplified.