The　microscale　heat　transfer　is　an　important　cooling　technique　developed　in　recent　years　and　applied　widely　to　cool　the　Large　Scale　Integrated　Circuit.　The　heat　accumulation　is　a　bottleneck　for　increasing　the　power　of　laser　systems,　for　example,　the　heat　flux　can　sometimes　reach　400　W/cm2　on　the　surface　of　a　10　mm　×　1　mm　diode　laser　bar.　In　the　paper,　the　structure　of　a　copper　heat　sink　for　cooling　high-power　diode　laser　bar　is　optimized.　Water　is　used　as　a　coolant.　The　result　shows　that　the　structure　of　microchannel　heat　sink　is　important　to　affect　the　thermal　resistance,　pump　power　and　temperature　distribution　on　the　surface　of　high-power　diode　laser　bar.　And　the　most　important　effect　on　the　pump　power　is　the　widths　of　the　microchannel　inlet　and　outlet.