In　this　work,　a　microchannel　heat　sink　with　trapezoidal　rib　walls　(TRAM),　in　which　walls　are　partially　made　of　trapezoidal　ribs　by　MEMS　(Microelectrical　Mechanical　System)　technique　are　put　forward.　The　influences　of　mass　flux,　heat　flux　and　exit　vapor　quality　on　flow　pattern,　boiling　curving,　heat　transfer　coefficient　(HTC),　two-phase　pressure　drop,　and　wall　temperature　characteristics　of　TRAM　are　investigated　and　the　traditional　rectangular　microchannel　heat　sink　(RECM)　is　as　the　reference.　Experiments　are　carried　out　using　pure　acetone　liquid　with　the　mass　flux　from　255　to　843　kg/(m2　&　sdot;s)　and　heat　flux　from　10　to　132　W/cm2.　The　results　show　that　the　onset　of　nucleate　boiling　(ONB)　of　TRAM　increase　with　the　increase　of　mass　flux.　The　HTC　of　TRAM　is　larger　than　that　of　RECM　whether　at　low　or　high　heat　flux.　The　pressure　drop　of　TRAM　increases　more　significantly　with　increasing　heat　flux　and　vapor　quality.　At　the　same　time,　the　pressure　drop　of　TRAM　is　lower　than　that　of　RECM.　The　flow　instability　is　more　moderate　at　a　larger　mass　flux　and　heat　flux　owing　to　the　more　uniform　bubble　size　and　bubble　distribution.