The　performance　of　the　heat　pump　can　be　improved　further　when　running　under　low　temperature　conditions　when　an　ejector　is　used　in　a　heat　pump　system　coupled　with　economized　vapor　injection　(EVI)　scroll　compressor.　In　this　paper,　the　design　method　of　the　heat　pump　system　with　ejector　(EVIe)　is　presented,　and　the　process　for　designing　the　heat　pump　with　ejector　has　been　summarized.　The　optimal　location　of　the　vapor　injection　inlets　is　at　the　place　where　the　vapor　can　inject　into　the　working　chambers　when　they　just　be　closed.　The　reasonable　value　for　the　entrainment　ratio　u　of　the　ejector　is　between　0.1　and　0.2.　One　prototype　heat　pump　was　designed　under　the　condition　of　the　evaporation　temperature　of　-20　degrees　C,　and　an　experimental　setup　was　established　to　test　the　prototype.　The　measured　results　demonstrated　that　the　heating　EER　of　the　heat　pump　system　with　ejector　could　reach　about　4%　higher　than　that　of　the　system　without　ejector　when　the　heating　capacity　remained　nearly　constant.　(C)　2010　Elsevier　Ltd　and　IIR.　All　rights　reserved.