With　deionized　water　as　working　fluid,　experiments　on　fluid　flow　and　heat　transfer　enhancement　characteristics　were　conducted　in　the　parallel-microchannel　silicon　heat　sink　with　expansion-constriction　cross　sections.　Based　on　the　microscale　heat　transfer　enhancement　mechanism,　two　parallel-microchannel　silicon　heat　sink　with　expansion-constriction　cross　sections　were　designed　and　processed.　In　contrast　to　the　corresponding　conventional　rectangular　microchannel　heat　sink,　the　flow　and　heat　transfer　parameters　of　parallel-microchannel　silicon　heat　sink　with　expansion-constriction　cross　sections　were　obtained　in　different　volume　flow　rates　and　constant　wall　heat　flux,　along　with　simultaneous　measurement　of　volume　flow　rate,　pressure　drop　and　temperature　in　the　inlet　and　outlet,　and　wall　temperature　at　the　substrate　of　heat　sink.　It　is　found　that　the　heat　transfer　rate　of　parallel-microchannel　silicon　heat　sink　with　expansion-constriction　cross　sections　is　increased　by　12.5%-85.1%　over　the　rectangular　straight　microchannel　heat　sink　value,　but　the　friction　factor　is　only　increased　by　-9.2%-31　4%,　showing　that　the　parallel-microchannel　silicon　heat　sink　with　expansion-constriction　cross　sections　has　superior　heat　transfer　enhancement　characteristics.