Plane　transformers　are　vital　components　of　high-frequency　power　electronic　converters,　and　the　calculation　and　optimal　design　of　their　parallel　winding　losses　pose　significant　challenges　in　the　design　process.　This　article　proposes　a　theoretical　calculation　method　for　winding　losses　based　on　impedance　matrix　and　circuit　equations,　and　it　derives　the　significance　and　acquisition　methods　of　impedance　matrix　parameters　under　high-frequency　conditions.　Building　upon　the　proposed　theoretical　calculation　method　for　winding　losses,　the　article　performs　classification　analysis　of　circuit　equations　to　determine　the　constraints　of　the　optimization　problem.　It　establishes　a　mathematical　model　for　optimizing　winding　losses　in　a　single　topology　and　provides　a　general　solution　method　for　designing　the　optimal　structure　of　winding　losses.　Finally,　experimental　measurements　are　conducted　to　validate　the　effectiveness　of　the　optimization　method　presented　in　this　article.　©　2023　IEEE.