For　the　problems　of　inaccurate　single　design　and　long　design　cycle　caused　by　multiple　design　debugging　in　the　traditional　EMI　filter　design　method,　a　new　method　for　efficient　design　of　EMI　filter　based　on　impedance　extraction　from　noise　source　was　proposed.　Firstly,　in　the　new　method　the　impedance　amplitude　and　phase　of　the　noise　source　was　obtained　accurately　and　quickly　by　inserting　the　passive　two-port　network.　Secondly,　the　EMI　filter　topology　was　selected　according　to　the　impedance　mismatch　principle;　then　it　was　comprehensively　considered　the　noise　source　impedance,　the　equivalent　load　impedance　at　the　LISN　end　and　the　influence　of　the　high-frequency　distribution　parameters　of　the　EMI　filter　on　the　insertion　loss　of　the　filter,　so　that　the　theoretical　insertion　loss　of　the　filter　is　equal　to　the　insertion　loss　required　in　the　conducted　EMI　test　band　range,　and　the　accurate　parameters　of　each　component　of　the　filter　were　obtained,　and　the　accurate　design　of　the　EMI　filter　was　realized.　Finally,　an　LED　drive　power　supply　was　used　for　the　experiment,　the　experimental　results　show　that　the　proposed　method　can　meet　the　expected　effect　in　one　design,　which　verifies　accuracy　and　efficiency　of　the　proposed　method.　©　2023　Editorial　Department　of　Electric　Machines　and　Control.　All　rights　reserved.