The　uniformity　of　polarization　distribution　in　the　cross　section　of　the　beam　is　a　key　factor　affecting　the　quality　of　the　radially　polarized　beam　and　its　practical　application.　The　polarization　purity　of　the　radially　polarized　beam　was　measured　and　compared　by　the　PBS　measurement　method,　the　slit　method　and　the　S　-wave　plate　method,　the　uniformity　of　the　polarization　state　of　the　radially　polarized　beam　in　the　cross　section　was　analyzed.　In　the　process　of　measuring　the　radially　polarized　beam　by　the　PBS　measurement　method　and　the　slit　method,　the　expression　of　the　radial　polarization　purity　was　given,　and　the　purity　of　the　radially　polarized　beam　was　determined　to　be　93.　4%　and　84.　1%,　respectively.　And　the　variance　formula　was　used　to　evaluate　uniform　distribution　of　the　radial　polarization　states.　Among　them,　the　PBS　measurement　method　expressed　the　purity　of　the　radially　polarized　beam　more　accurately,　and　the　slit　method　can　reflect　the　polarization　distribution　characteristics　of　the　radially　polarized　beam　more　accurately　by　comparing　the　polarization　degrees　of　different　regions.　The　S-wave　plate　method　can　indirectly　measure　the　purity　of　the　radially　polarized　beam　using　the　existing　polarization　analyzer　in　the　market,　and　is　more　suitable　for　measuring　the　change　of　the　polarization　state　of　the　radially　polarized　beam　during　the　amplification　process.　©　2019,　Editorial　Board　of　Journal　of　Infrared　and　Laser　Engineering.　All　right　reserved.