The　winding　loss　of　the　wireless　power　transfer　(WPT)　magnetically-coupled　system　is　an　important　part　that　affects　the　efficiency　of　the　WPT　system.　However,　there　needs　to　be　an　effective　evaluation　method　for　winding　loss　(especially　the　winding　loss　of　the　Litz　wire).　This　paper　proposed　a　new　method　for　evaluating　the　winding　AC　resistance.　In　this　method,　the　electrical　parameters　of　the　WPT　magnetically-coupled　system　were　measured　by　a　small　signal　instrument.　The　separation　of　the　winding　AC　resistance　and　the　additional　core　loss　resistance　under　the　measurement　excitation　signal　was　realized　by　core　loss　model　calculation　or　finite　element　analysis　(FEA)　simulation.　This　method　was　suitable　for　evaluating　the　winding　AC　resistance　of　the　WPT　magnetically-coupled　system　and　the　air-gap　inductor.　The　error　between　the　FEA　simulation　results　based　on　the　3-D　air-gap　inductor　and　the　evaluation　results　of　this　method　was　less　than　5%,　which　verified　the　proposed　method.　Finally,　a　2kW　WPT　system　prototype　was　built,　and　the　correctness　of　Litz　coil　AC　resistance　extraction　was　verified　by　differential　power.　©　2022　Chinese　Machine　Press.　All　rights　reserved.