In　this　paper,　an　integrated　gas-injected　scroll　compressor　heat　pump　system　using　R1234yf,　R32　and　its　binary　mixtures　as　working　fluid　was　developed　and　their　heating　performances　under　low　ambient　temperature　were　quantitatively　evaluated.　A　composite　test　system　consisting　of　second-refrigerant　calorimeter　and　water-cooled　condenser　was　used　to　test　the　system　working　performance.　The　condensing　temperature,　evaporating　temperature,　compressor　power　input　and　other　variables　were　analyzed　to　evaluate　the　system　heating　capability　and　energy　efficiency.　Test　results　showed　that　the　R1234yf　system　can　run　at　an　evaporating　temperature　of　-25　degrees　C.　R1234yf/R32　mixture　can　run　at　an　evaporating　temperature　of　-20　degrees　C　and　it　has　the　highest　heating　COP　value　among　other　refrigerants;　R1234yf/R32　gas　injection　system　provided　very　significant　performance　improvements　for　heating　performance,　compared　with　no　gas　injection,　the　heating　capacity　and　heating　COP　can　improve　16%similar　to　20%　and　13%similar　to　16%,　respectively.　(C)　2017　Elsevier　Ltd　and　IIR.　All　rights　reserved.