According　to　the　nonlinear　polarization　rotated　effect,　a　self-starting　mode-locked　ring　cavity　fiber　laser　is　obtained　and　optimized　through　changing　the　fiber　length　and　coupler　parameters.　As　the　seed　of　an　all-fiber　ultra-short　pulse　amplifier　with　master　oscillator　power　amplifier　(MOPA)　structure,　the　pulse　which　has　2.042　W　in　average　power,　1063.8　nm　in　wavelength,　41.3　MHz　in　repetition　frequency,　45　ps　in　impulse　duration,　49.4　nJ　in　single　pulse　power　and　1.1　kW　in　peak　power,　is　realized,　taking　double-cladding　fiber　as　the　gain　medium.　The　optical　conversion　efficiency　of　the　whole　system　is　40.8%,　which　could　be　supportable　to　the　higher　power　all-fiber　pulse　laser.