The　multiphysics　numerical　model　for　the　thermoelectric　power　generator　(TEG)　is　established.　The　influence　of　heat　exchanger　is　fully　considered.　The　characteristics　of　temperature　distribution,　pumping　power　and　thermal　conversion　efficiency　of　the　TEGs　with　different　fin　structures　are　studied　at　Reynolds　number　from　1000　to　10000.　Three　types　of　fins　including　the　full-height　plate　fin　(Fin-1),　gradient　fin　emphasizing　downstream　enhancement　(Fin-2),　and　gradient　fin　emphasizing　upstream　enhancement　(Fin-3)　are　compared　and　analyzed.　The　result　shows　that,　with　a　constant　length-to-height　ratio　of　hot-side　channel　and　coverage　rate　of　thermoelectric　materials,　the　output　power　and　conversion　efficiency　of　the　TEG　show　a　quadratic　changing　trend　with　the　flow　rate,　and　the　optimal　matching　flow　rate　makes　the　system　have　the　best　power　generation　performance.　The　full-height　plate　fin　is　sensitive　to　the　change　of　flow　rate.　With　the　increase　of　flow　rate,　the　pressure　loss　increases,　resulting　in　no　benefit　for　the　net　output　power　and　conversion　efficiency.　In　comparison,　the　heat　exchanger　with　gradient　fin　can　generate　positive　benefits　in　a　larger　range.　The　heat　exchanger　with　Fin-2　has　the　best　streamwise　temperature　uniformity,　but　the　local　thermal　resistance　along　the　channel　is　the　largest.　Based　on　the　performance　of　the　local　thermal　resistance　distribution　and　pumping　power　consumption,　the　TEG　system　with　Fin-3　has　the　highest　net　conversion　efficiency,　so　the　synthesis　factor　of　the　local　thermal　resistance　distribution　and　pumping　power　is　the　key　to　the　optimal　design　of　heat　exchanger　in　TEGs.　©　2020,　Science　Press.　All　right　reserved.