Abstract: In order to generate radially polarized beams, a method of polarization shaping of linearly polarized beams outside the cavity by a combined half-wave-plates and a combined linear polarizer was put forward. In order to detect the performance of the generating system, the polarization distribution of the output beam was detected by the rotary polarizer method, and its polarization purity was calculated by the classical stokes parameters measurement method. Finally, based on the Mach-Zehnder interference principle, the linear polarization phase relationship of the symmetric region of the radially polarized beams was detected. The results show that when the combined linearly polarizer is divided into four segments, the radially polarized beams with a polarization purity of 80.5% is obtained, and the linear polarization phase difference of the symmetric region is π. The result is helpful to produce the radially polarized light with high purity at low cost.