Aiming at the uneven heat dissipation induced by the uneven water channel flow of microchannel-heat sink for original curamik, the numerical simulation based on FLUENT software is carried out. Optimization scheme is proposed from the aspect of internal structure and the heat sink material. The influence of the microchannel width, interval and microchannel ridge length on the chip surface temperature rise and pressure drop are obtained, when the heat sink height and the width of the import and export are invariant. Based on the optimized parameters, the pure Ni microchannel heat sink is manufactured by selective laser melting technology, and the chip is packaged and tested. The results show that thermal resistance of microchannel heat sink reaches 0.39 K/W, the pressure drop reaches 140 kPa, which can meet the need of 80 W semiconductor laser cooling requirements.