With　the　increasing　complexity　of　power　system,　higher　requirements　are　put　forward　for　the　performance　and　stability　of　electromagnetic　switch,　and　PWM　high　frequency　control　has　become　a　development　trend.　Under　the　PWM　high　frequency　control　mode,　the　proximity　effect　and　skin　effect　make　the　current　density　distribution　in　the　conductor　uneven,　which　increases　the　winding　loss.　If　it　works　for　a　long　time,　it　will　lead　to　the　increase　of　local　heating　value　and　reduce　the　service　life　of　the　electromagnetic　switch.　Based　on　the　actual　winding　model　of　electromagnetic　switch,　this　paper　applies　Dowell　algorithm　and　improved　Dowell　algorithm　to　analyze　the　eddy　current　effect　in　winding.　Through　the　algorithm,　the　relationship　between　the　working　frequency　of　electromagnetic　switch,　winding　thickness,　AC　resistance　and　penetration　rate　is　revealed,　and　the　optimal　winding　thickness　at　a　specific　working　frequency　is　deduced.　Finally,　the　actual　winding　is　measured　by　impedance　analyzer,　and　the　calculation　errors　of　analytical　algorithm　and　measured　winding　are　compared.　Experiments　show　that　the　improved　Dowell　algorithm　has　high　accuracy　in　calculating　the　high-frequency　winding　loss　of　electromagnetic　switch,　which　provides　reference　for　the　optimal　design　of　electromagnetic　switch　winding.　©　2023　IEEE.