An　all-fiber　structure　nanosecond　pulse　fiber　laser　was　designed　and　its　configuration　was　introduced.　It　took　an　adjustable　acousto-optic　Q-switch　as　the　modulator　and　double-cladding　Yb3+-doped　fibers　as　gain　media　in　the　resonator.　Through　optimizing　some　system　factors,　such　as　the　length　of　gain　fiber　and　the　reflectivity　of　a　cavity　mirror,　a　stable　nanosecond　pulse　was　gotten,　which　had　1.3　W　average　power,　1064　nm　wavelength,　11　kHz　repetition　frequency,　150　ns　impulse　duration,　0.12　mJ　single　pulse　power　and　0.8　kW　peak　power.　The　optic-optic　conversion　efficiency　of　the　system　is　30%.　The　optimized　fiber　laser　can　be　a　seed　source　applying　to　a　fiber　amplifier　with　the　Master　Oscillator　Power　Amplifier　(MOPA)　configuration　to　achieve　high　power　outputs.