Based　on　the　operation　testing　of　new　air-water　double　source　composite　heat　pump　system　(AWDSHPS-N),　three　defrosting　modes　were　investigated　under　the　same　ambient　condition,　which　included　the　condenser　outlet　refrigerant　recooling　defrosting(D-I),　the　low　temperature-hot　water　defrosting(D-II),　the　condenser　outlet　refrigerant　recooling　and　low　temperature-hot　water　defrosting　at　same　time　(D-).　Total　coefficient　of　performance　(COP)　of　AWDSHPS-N　was　used　to　evaluate　the　influence　of　the　three　modes.　The　influence　on　the　total　COP,　defrosting　operating　characteristics　and　energy　consumption　of　D-I,　D-II　and　D-　were　discussed　and　compared　with　those　in　the　reverse-cycle　defrosting　mode,　under　the　same　ambient　condition.　The　results　of　test　conditions　indicated　that　for　D-I　and　D-II,　the　total　COP　can　be　decreased　by　0.42%　and　3.93%,　respectively,　compared　with　the　COP　of　frosting　period.　The　heating　power　and　COP　during　D-II　defrosting　were　27.4%　and　17.8%　higher　than　those　of　frosting　operation,　respectively.　The　total　COP　of　AWDSHPS-N　choosing　D-I,　D-II　and　D-　were　26.06%,　29.79%　and　17.02%　higher　than　that　of　verse-cycle　defrosting,　and　the　defrosting　energy　consumption　of　D-I,　D-II　and　D-　were　only　3.11%,　34.78%　and　28.26%　of　the　reverse-cycle　defrosting　energy　consumption.　©　2018,　Science　Press.　All　right　reserved.