For　the　inductor　with　air　gap,　the　magnetic　field　distribution　in　winding　window　is　quite　complex　due　to　the　air-gap　fringing　effects　of　the　core.　The　Dowell　model　which　is　effectively　used　in　the　calculation　of　AC　winding　losses　in　transformers　is　no　longer　valid　for　gapped　inductors.　In　this　paper,　the　air-gap　is　equivalently　replaced　by　surface　current　with　certain　geometry　and　current　density　distribution.　And　then,　mirror-image　method　is　utilized　to　deal　with　the　boundary　effect　of　magnetic　core　with　high　permeability.　Most　important,　an　novel　analytic　method　is　also　proposed　to　improve　the　calculation　speed　and　accuracy　of　high-frequency　losses　of　round　conductor　within　wider　frequency　range.　Finally,　the　method　proposed　is　verified　by　FEM　(finite　element　method)　simulation.　It　keeps　very　low　error,　which　is　less　than　8%,　when　the　ratio　of　wire　diameter　to　skin　depth　reaches　4.5.　©　2018,　Ubiquitous　International.　All　rights　reserved.