Winding　eddy　current　loss　of　the　transformer　in　flyback　converter　is　one　of　the　research　focus　in　winding　techniques　of　high-frequency　power　magnetic　components.　Based　on　the　reviewing　for　the　previous　researches,　the　winding　loss　mechanism　of　the　transformer　is　analyzed　deeply　through　decomposition　of　winding　current　and　Finite　Element　field　simulation.　And　it　is　found　that　the　magnetic　fields　inducing　the　total　winding　loss　have　both　behaviors　with　inductor＇s　and　transformer＇s　field.　With　this　understanding,　the　techniques　for　reducing　the　winding　loss　are　researched　to　conclude　that　the　effectiveness　of　the　techniques　depends　on　the　magnetic　field　constitutes　in　winding　window.　Moreover,　a　new　analytical　model　for　the　transformer　winding　loss　in　flyback　converter　is　also　proposed　by　utilizing　the　orthogonality　of　the　two　field　components.　The　research　results　are　approved　by　finite　element　simulation.　©　2009　Chin.　Soc.　for　Elec.　Eng.