Planar　PCB　magnetic　elements　have　become　increasingly　popular　in　the　design　of　wide-band-gap　converters　based　on　SiC　and　GaN　to　reach　a　higher　power　density.　The　parasitic　capacitance　in　planar　transformers　often　cannot　be　ignored　because　of　the　large　area　of　copper　and　the　very　thin　dielectric　between　PCB　layers.　A　multi-conductor　distributed　capacitance　equivalent　model　for　planar　transformer　is　proposed　in　this　paper　to　establish　a　more　accurate　high　frequency　model　for　wide-band-gap　converters　which　have　planar　transformer.　The　3D　winding　structure　of　planar　transformer　can　be　converted　into　2D　circuit　model　through　finite　element　simulation　and　numerical　analysis.　Two　GaN-based　experimental　prototype　with　switching　frequencies　of　500　kHz　and　1　MHz　respectively　are　built　and　tested　in　order　to　verify　the　accuracy　of　the　multi-conductor　distributed　capacitance　model.　The　experimental　results　show　that　the　trend　of　common-mode　EMI　spectrum　distribution　predicted　by　the　multi-conductor　capacitance　model　is　closer　to　the　measured　spectrum　than　which　predicted　by　traditional　one-capacitor　model,　and　its　amplitude　error　can　be　basically　kept　within　10dBμV.　©　2021　IEEE.