We　demonstrate　a　high-power,　high　signal-to-noise　ratio　single-frequency　1　mu　m　Brillouin　all-fiber　laser　with　high　slope　efficiency.　The　Brillouin　laser　system　consists　of　a　high-power　single-frequency　fiber　laser　and　a　single-pass　Brillouin　ring　cavity.　The　high-power　single-frequency　fiber　laser　is　one-stage　master-oscillator　power　amplifier　with　the　maximum　output　power　of　10.33　W,　the　signal-to-noise　ratio　of　50　dB　and　the　slope　efficiency　of　46%.　The　Brillouin　fiber　laser　is　pumped　by　the　amplified　laser　with　a　linewidth　of　33　kHz　and　an　output　power　of　2.61　W　limited　by　the　damage　threshold　of　the　optical　isolator.　By　optimizing　the　length　of　the　Brillouin　ring　cavity　to　10　m,　stable　single-frequency　Brillouin　fiber　laser　is　obtained　with　3　kHz　linewidth　owing　to　the　linewidth　narrowing　effect.　At　the　launched　pump　power　of　2.15　W,　the　Brillouin　fiber　laser　generates　maximum　output　power　of　1.4　W　with　a　slope　efficiency　of　79%　and　the　optical　signal-to-noise　ratio　of　77　dB.