Abstract: Structural parameters of microchannel heatsink such as thickness of the front wall and width of the turn-over channel are optimized through numerical calculation based on general industrial processing.And copper microchannel heatsinks are fabricated by using photophobia,chemical etch and diffusion welding technology.Semiconductor laser bars,with cavity length of 1 mm,emitter width of 200 μm and 50% of fill-factors are packaged on the presented microchannel heatsinks and tested.With an exterior size of 27 mm×11 mm×1.5 mm,thermal resistance of microchannel heatsink reaches 0.34 K/W,which meets the need of cooling of high power semiconductor laser bars.