Previous　transformer　electromagnetic　interference　(EMI)　models　only　take　into　account　the　capacitance　effect,　which　is　good　in　evaluating　the　EMI　characteristic　in　lower　frequency　ranges.　However,　the　errors　become　large　between　model　analysis　and　experiment　results　in　higher　frequency　ranges.　The　analysis　of　the　mechanism　in　the　transformer　shows　that　the　conducted　EMI　characteristic　is　affected　by　both　stray　electric　and　magnetic　fields.　The　leakage　magnetic　field　has　an　obvious　effect　on　the　impedance　of　common-mode　(CM)　conduction　path.　Based　on　the　above　analysis,　a　comprehensive　transformer　model　for　conducted　CM　noise　characteristic　was　build　by　taking　into　account　both　the　effect　of　distributed　electrical　field　and　leakage　magnetic　field.　The　new　model　indicates　that　the　resonance　between　leakage　magnetic　field　and　the　equivalent　inductive　and　capacitive　parameters　of　stray　field　are　the　key　factors　to　affect　EMI　characteristic　in　high-frequency　ranges　for　a　transformer.　The　results　of　insert　loss　tests　verify　that　the　new　model　can　improve　the　prediction　precision　and　evaluation　effect　in　higher　frequency　ranges.　©　2017　Chin.　Soc.　for　Elec.　Eng.