CVBs　(cylindrical　vector　beams)　are　widely　used　in　optical　imaging,　optical　trapping,　material　processing,　etc.　In　this　study,　based　on　mode-selective　couplers　and　passive　mode-locking　fiber　technology,　a　cylindrical　vector　fiber　amplifier　with　an　MOPA　(master　oscillator　power　amplifier)　structure　was　developed.　In　the　experiment,　the　pre-amp　stage　reached　19.87　mW　output　power　and　a　CVB　output　with　a　mode　purity　greater　than　97%.　The　measured　beam　quality　factor　was　M2　=　2.1.　The　CVB　output　power　obtained　by　the　first-amp　stage　was　152.4　mW,　and　the　mode　purity　was　greater　than　92%.　The　measured　beam　quality　factor　was　M2　=　1.99.　The　internal　inhomogeneity　and　external　effects　of　the　isotropic　LMA　(large-mode-area)　fiber　led　to　a　decrease　in　beam　quality　and　mode　purity.　After　amplification,　the　gain　of　the　fundamental　mode　was　higher　and　the　power　was　greater,　resulting　in　a　greatly　reduced　mode　purity.　This　CVB　fiber　amplifier　yielded　important　research　value　in　expanding　the　applications　of　high-power　fiber　lasers.