A　nanosecond　fiber　laser　with　a　line　cavity　was　developed　by　taking　a　acousto-optic　Q-switch　as　the　modulator　and　a　single　cladding　Yb-doped　fiber　as　the　gain　medium.　Then,　by　optimizing　the　laser,　a　nanosecond　pulse　seed　source　was　obtained.　With　all-fiber　Master　Oscillator　Power　Amplifier　(MOPA),　the　nanosecond　pulse　was　amplified　by　one　stage　and　obtained　pulse　laser　shows　its　average　power　in　10.10　W,　wavelength　in　1064　nm,　repetition　frequency　in　11　kHz,　impulse　duration　in　150　ns,　single　pulse　power　in　0.92　mJ　and　peak　power　in　6　kW.　Moreover,　the　optical-optical　conversion　efficiency　is　67%.　The　whole　system　involves　just　a　one-stage　amplifier,　which　promotes　the　pumping　efficiency　and　reduces　the　cost.