An　experimental　investigation　has　been　carried　out　to　analyze　the　flow　and　heat　transfer　characteristics　in　the　silicon　microchannel　heat　sinks　with　periodic　jetting　or　throttling　structures　by　using　deionized　water　with　flow　rates　of　28-95　ml/min.　The　heat　sink　includes　10　parallel　microchannel　with　49　identical　units　(jetting　or　throttling　structures)　long　the　flow　direction,　width　of　100-200　mu　m,　depth　of　215　mu　m.　Results　show　the　heat　transfer　of　throttling　microchannel　heat　sink　is　enhanced　obviously　albeit　with　larger　pressure　drop　penalty.　It　is　because　that　the　fluid　is　completely　blocked　by　the　sudden　contractible　structure,　then　forms　the　severe　reflux　to　wash　divergent　structure　and　enhance　fluid　mixing.　Compared　with　jetting　microchannel　heat　sink,　the　Nu(av)　of　throttling　microchannel　heat　sink　is　improved　to　1.56-1.29　times　albeit　with　f　increased　to　1.84-1.51　times　with　increasing　of　flow　rates.　But　the　total　performance　evaluation　criterion　(PEC)　is　increased　to　about　2.5　times.　For　maximum　temperature　＜　60　degrees　C,　the　required　minimum　flow　rates　of　throttling　microchannel　heat　sink　are　reduced　obviously.　Even　the　pumping　power　of　that　is　increased　at　heater　power　larger　than　50　W,　the　thermal　resistance　is　reduced　severely.　It　means　the　throttling　microchannel　heat　sink　can　meet　larger　heater　power　with　lower　flow　rates　in　application.