Abstract: A multi-usage connecting mechanism of pneumatic tool, including a connecting member and a supporting member. One end of the connecting member is formed with a right polygonal stem and the connecting member is formed with a through hole about an axis thereof. An annular groove is formed on the connecting member between two ends thereof. A circular tube extends from one end of the stem of the connecting member along the axis thereof. An inner side of the circular tube is formed with inner thread screwing with outer thread of the supporting member. The supporting member is a circular tube member. Bearings are disposed in the supporting member. One end of the supporting member is formed with outer thread. The other end of the supporting member is formed with a stopper section for stopping the bearings.