Experiments　on　friction　factor　and　heat　transfer　performances　are　conducted　in　a　trapezoidal　silicon　microchannel　heat　sink　with　deionized　water　as　working　fluid.　The　flow　and　heat　transfer　parameters　are　obtained　in　different　volume　flowrate　and　different　heat　flux,　along　with　simultaneous　measurement　of　the　pressure　and　temperature.　It　is　found　that　the　heat　transfer　characteristics　in　trapezoidal　silicon　microchannels　deviated　from　theoretical　predictions　for　conventional　channels.　The　corner　between　the　side　wall　and　the　bottom　wall　has　an　significant　influence　on　the　flow　and　heat　transfer　performances.　Based　on　the　test　results,　a　modified　relation　for　the　heat　transfer　characteristics　of　trapezoidal　silicon　microchannel　heat　sink　is　obtained.