A　new　type　of　heat-moisture　treatment　air　conditioner　terminal　unit　(ACTU)　for　heating,　cooling　and　dehumidification　is　designed　by　using　a　parallel　flow　tube　as　the　core　element,　attached　to　closed　rectangular　fins,　and　its　performance　and　resistance　characteristics　are　studied.　The　research　results　show　that　under　indoor　temperature　conditions　in　winter　and　summer,　when　the　water　supply　temperature　is　60　and　7 °C,　the　circulating　water　flow　is　0.5　m3/h,　and　the　air　volume　is　150　m3/h,　then　the　heat　supply,　cooling　capacity　and　the　dehumidification　capacity　can　reach　758　W,　662　W　and　721 g/h,　respectively.　The　maximum　resistance　on　the　water　and　the　air　side　is　4.66 kPa　and　27.2 Pa,　respectively.　The　thermal　resistance　of　the　ACTU　is　analyzed,　and　the　performance　optimization　design　is　carried　out.　The　results　provide　a　theoretical　basis　for　the　application　and　optimization　of　the　ACTU.　©　2023,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.