Flow　characteristics　in　channels　with　micron　dimension　are　different　from　macroscale　channels,　which　mainly　embodies　three　aspects　friction　factor,　transition　Reynolds　number　and　Poiseuille　number.　With　this　background,　the　flow　characteristics　of　water　were　experimentally　investigated　in　rectangular　silicon　microchannels　with　hydrodynamic　diameter　ranging　from　167　μm　to　195　μm　and　168　μm　to　399　μm　for　circular　glass　microtubes.　The　experimental　results　show　that　the　values　of　the　critical　Reynolds　number　fall　between　1300　and　1480　in　rectangular　microchannels　with　the　hydrodynamic　diameter　of　167　μm　to　195　μm　while　falling　between　2600　and　2850　in　circular　microtubes　with　the　hydrodynamic　diameter　of　168　μm　to　399　μm;　Besides,　the　friction　factor　and　Poiseuille　number　of　both　rectangular　microchannels　and　circular　microtubes　are　consistent　with　the　theoretical　values,　which　indicates　geometric　features　have　no　significant　influence　on　flow　resistance.　The　entrance　length　in　channel　S-3　with　length-diameter　ratio　of　173　is　slightly　more　than　that　of　conventional　channel,　which　shows　that　the　entrance　effect　is　obvious　in　micro-scale　channel.　Investigation　of　the　relationship　of　local　resistance　versus　the　flow　rate　in　rectangular　silicon　microchannel　shows　good　agreement　between　theoretical　curves　and　experimental　results.　©　2012　Chinese　Society　for　Electrical　Engineering.