The invention provides a pneumatic type rapier weaving machine and belongs to the technical field of textile machinery. A weft insertion mechanism of the pneumatic type rapier weaving machine comprises a cylinder body and a cylinder rod. A round pillar cavity is processed in the inner portion of the cylinder body. An exit of the cylinder is provided with a sliding plug which is assembled through air impermeability. One end of the cylinder rod penetrates through the sliding plug, extends into the inner portion of the round pillar cavity and is assembled with the inner wall of the cylinder body through air permeability. The other end of the cylinder rod is assembled with a weft sending block. Two ends of the cylinder body are respectively provided with an air hole which is communicated with the round pillar cavity and the round pillar cavity is arranged in the inner portion of the cylinder body. The weft insertion mechanism utilizes gas to push the cylinder rod, and the weft sending process is accomplished by connecting the weft sending block through the cylinder rod. Compared with an ordinary rapier weft sending structure, the pneumatic type rapier weaving machine is simple in structure, easy to design, manufacture and assemble and is connected into a control system due to the adoption of pneumatic control.