In　order　to　improve　many　disadvantages　that　the　heat　pump　system　has　when　it　uses　the　reverse-cycle　defrosting　method　in　the　low　temperature　environment,　a　new　air-water　double　source　composite　heat　pump　system　(AWDSHPS-N)　was　presented.　This　system　has　a　new　preheating　and　defrosting　function.　AWDSHPS-N　has　defrosted　for　5　min　and　has　5　different　defrosting　ways,　such　as　the　condenser　outlet　refrigerant　recooling　defrosting,　the　low　temperature-hot　water　defrosting,　and　so　on.　It　can　be　put　into　different　modes　by　changing　some　relevant　valves　or　starting　and　stopping　the　pump　of　the　low　temperature　water.　In　this　way,　the　heat　output　power　of　AWDSHPS-N　may　be　reduced　dramatically,　but　the　system　can　produce　heating　continuously.　A　test-bed　including　constant　temperature　and　humidity　environment　storehouse　and　a　low　temperature　water　tank　were　set　up　to　get　operating　data　for　coefficient　of　performance　(COP)　of　AWDSHPS-N.　The　environment　storehouse　imitates　the　change　in　outdoor　environment　by　keeping　the　temperature　and　the　humidity　at　a　certain　level　constantly,　and　the　low　temperature　water　tank　with　two　electric　heating　bars　can　be　thought　as　a　low　temperature　heating　source　of　a　solar　energy　system　or　a　waste　heat　system.　By　heating　the　water　from　18　to　51,　the　COP　of　AWDSHPS-N　was　tested　and　analyzed　in　air　source　heating　mode　(ASHM),　water　source　heating　mode　(ASHM),　water　source　heating　mode　(WSHM)　and　air-water　double　source　heating　mode　(AWSHM),　respectively.　By　calculating,　the　COP　of　AWSHM　is　6.1%-20.5%　higher　than　ASHM.　When　the　ambient　temperature　and　the　low　temperature　water　are　both　above　15,　the　COP　of　AWSHM　is　the　best　one,　and　the　COP　of　WSHM　is　the　last　one　among　these　three　heating　modes.　©　All　Right　Reserved.