A pneumatic-fixation connecting having a body, a movable part, a plurality of spheres, a plurality of elastic units, and a plurality of stop units is disclosed, wherein each of the elastic units is disposed between the body and the movable part via each of the stop units, respectively. When an external force is applied on the movable part, the distance between the movable part and the body is reduced and the sphere does not block the connecting pin in the extension tube inside the body. When the external force disappears, the distance between the movable part and the body increases such that the sphere affixes the connecting pin and the body. The stop unit can be used, not only to adjust the length and elastic force of the elastic unit so as to extend the life cycle of the elastic unit, but also to help in changing the elastic unit which in turn enhances the efficiency of the replacement work.