This　work　experimentally　studied　the　single-phase　flow　and　heat　transfer　characteristics　of　a　type　of　multiport　microchannel　flat　tube　(MMFT)　with　a　sawtooth　fin　structure.　This　MMFT　consisted　of　numerous　parallel　rectangular　microchannels　and　is　widely　used　in　industry　as　the　heat　transfer　unit　of　a　heat　exchanger.　Three　samples　with　different　dimensions　and　varied　fin　sizes　were　used　as　test　sections　to　perform　the　experiment　with　water　as　a　working　fluid.　The　Reynolds　number　was　varied　from　110　to　6100　to　cover　the　laminar,　transition,　and　early　fully　developed　turbulent　regions.　Moreover,　a　smooth　MMFT　of　the　same　dimension　as　one　of　the　three　samples　with　a　fin　structure　was　tested　as　the　control　experiment.　The　experimental　results　show　that　the　fin　structure　can　enhance　the　heat　transfer　at　the　expense　of　increasing　the　pressure　drop　and　earlier　induction　of　the　laminar　turbulent　transition.　The　degree　of　heat　transfer　enhancement　and　the　pressure　drop　increase　both　depend　on　the　raised　degree　of　the　fin　structure.　Finally,　the　performance　evaluation　criterion　(PEC)　was　calculated　to　comprehensively　assess　the　performance　of　the　MMFT　with　fins.　The　values　of　the　PEC　indicate　that　the　MMFT　with　fins　improves　the　heat　transfer　performance.　(C)　2014　Elsevier　Masson　SAS.　All　rights　reserved.