The　geometric　effects　on　the　liquid　flow　were　investigated　in　microchannel　based　on　the　numerical　simulation　method.　Effects　of　geometry　were　shown　obviously　on　the　microflow　by　comparing　the　results　of　different　geometric　characteristics　covering　hydraulic　diameter,　length　and　aspect　ratio.　Thermal　boundary　conditions　are　the　same　for　different　cases　in　the　numerical　simulation.　The　geometric　parameters　except　the　aspect　ratio　have　little　effect　on　the　friction　factor　but　all　of　them　obviously　make　the　Nusselt　number　changed.