This　study　demonstrates　the　use　of　a　Liquid　Crystal　Polymer　(LCP)　vortex　retarder-based　Yb-Doped　Fiber　(YDF)　MOPA　system　with　nanosecond　pulse　output　to　achieve　efficient　generation　of　a　radially　polarized　beam　from　fiber　lasers.　The　LCP　vortex　half-wave　plate　was　employed　as　a　mode　converter　after　the　MOPA　laser　to　efficiently　convert　the　high-peak-power,　narrow-linewidth,　linearly　polarized　nanosecond　Gaussian　pulse　signal　into　a　Laguerre-Gaussian　beam　with　a　hollow-ring　distribution　of　transverse　intensity　using　the　spatial　phase　conversion　method.　When　the　MOPA　system　consisted　of　a　narrow-linewidth　continuous　seed　source,　an　electro-optical　intensity　modulator　and　a　five-stage　YDF　amplifier　were　built　up.　A　stable　LP01　mode　output　with　an　average　power　of　20.1　W　was　obtained　from　the　MOPA　system.　Subsequently,　an　LCP　vortex　half-wave　plate　was　adopted　as　a　spatial　mode　converter　and　a　radially　polarized　beam　output　with　a　maximum　average　output　power　of　19.5　W,　pulse　width　of　10　ns,　and　perfect　hollow-ring　transverse　intensity　was　obtained　at　a　repetition　rate　of　10　kHz.　The　mode　purity　measured　by　the　PBS　method　is　about　88.5%,　which　indicates　that　the　radially　polarized　beam　obtained　has　the　advantages　of　high　efficiency　and　high　mode　purity.　This　work　can　establish　the　foundation　for　the　practical　and　highly　efficient　applications　of　radially　polarized　beams　in　the　field　of　optical　trapping,　high-resolution　imaging,　and　materials　processing.　©　2020,　Science　Press.　All　right　reserved.