The　efficient　use　of　energy　carried　by　low　temperature　flue-gas　is　a　hot　topic　of　energy　saving　in　thermal　power　plant.　The　thermodynamic　analyses　on　conventional　low　temperature　economizer　with　a　reference　case　of　1000　MW　supercritical　power　plant　were　carried　out.　Results　show　that　the　standard　coal　consumption　rate　for　power　generation　could　be　decreased　by　2.50　g·(kW·h)-1.　However　a　big　portion　of　exergy　was　destructed　in　air　pre-heater,　about　22.03%　to　the　total　exergy　put　into　the　air　pre-heater,　which　is　bigger　than　the　exergy　carried　by　the　boiler　exhaust.　Therefore,　a　waste　heat　utilization　system　integrated　with　SCO2power　cycle　was　proposed　in　this　paper,　which　is　designed　to　decrease　the　exergy　destruction　in　air　pre-heater.　Then　parameters　of　SCO2　power　cycle　were　optimized.　The　standard　coal　consumption　rate　for　power　generation　could　be　decreased　by　3.62　g·(kW·h)-1with　optimal　parameters.　The　standard　coal　consumption　rate　for　power　generation　could　be　further　decreased　by　5.58　g·(kW·h)-1when　low　temperature　economizer　were　also　integrated.　Finally　the　essential　reason　for　the　energy　saving　were　revealed　by　exergy　analysis.　©　2017,　Science　Press.　All　right　reserved.