A　new　type　of　air-source　heat　pump　system　with　liquid　subcooling　defrosting　(ASHPSD)　was　proposed,　in　which　a　hot　liquid　refrigerant　is　used　for　defrosting;　further,　the　outdoor　unit　of　the　system　comprises　multiple　evaporators.　In　the　process　of　frosting　and　defrosting,　a　finite-time,　steady-state　thermodynamic　method　was　adopted　to　establish　a　simulation　model　of　heat　and　mass　transfer.　Simulation　results　demonstrate　that　the　defrosting　performance　of　the　heat　pump　system　is　optimal　when　the　number　of　evaporators　is　four.　Furthermore,　the　heat　and　mass　transfer　in　the　process　of　frosting　and　defrosting　was　calculated,　particularly　the　variation　in　frost　layer　thickness　with　time.　An　experimental　apparatus　for　the　ASHPSD　system　was　developed,　following　which　its　defrosting　performance　was　experimentally　investigated.　Experimental　results　show　that　the　energy　efficiency　ratio　of　the　system　can　still　reach　2.32　when　the　outdoor　air　temperature　is　-　10celcius.