Microchannel heat sinks are minute channels fabricated onto the back of the thin silicon chip substrate with hydraulic diameter ranging from 10 to 103 μm. Microchannels have the advantage of large surface area to volume ratio, low thermal resistances and low flux, so they are thought to be an effective solution in dissipating thermal. One typical application is the cooling of the laser diode arrays. Because flow and heat transfer in microchannel are different from those in macro one, further research is necessary. An FEA (finite element analysis) model of a flat plate microchannel is set up in this paper using commercial software CoventorWareTM to investigate the localized flow and heat transfer in a single microchannel, computation results are also presented and analyzed. Microchannel is