Aiming　at　the　household　air　source　heat　pump　for　＇coal　to　electricity＇,　a　capillary　as　a　throttle　element　is　proposed　to　replace　the　thermal　expansion　valve　or　the　electronic　expansion　valve,　and　an　experimental　device　for　heat　pump　system　was　set　up.　The　influence　of　different　capillary　length　on　the　compressor　suction　pressure,　exhaust　temperature　and　heat　capacity　of　the　unit　under　variable　frequency　regulation　of　compressor　were　experimentally　studied.　The　experimental　results　show　that,　after　replacing　the　thermal　expansion　valve　or　the　electronic　expansion　valve,　the　system　can　run　stably　for　a　long　time.　The　system　has　the　best　thermal　performance　when　the　capillary　length　is　500　mm　and　the　compressor　frequency　is　35　Hz,　and　the　heating　capacity　and　heating　COP　are　the　largest,　but　the　suction　pressure　and　the　exhaust　temperature　are　moderate.　©　All　Right　Reserved.