In this paper, a three folds spatial resonator composed of a triple-axicon retroreflector and four pieces of quarter wave phase retarder is demonstrated to directly output radially polarized beams in a fast axial flow (FAF) CO2 laser system. The triple-axicon retroreflector serves as the azimuthally polarized beams' selective element, and the quarter wave phase retarders convert the azimuthally polarized beams to radially polarized beams. Finally, a stable 1.5 kW radially polarized beam is generated in this laser system.