With　the　continuous　improvement　of　the　power　density　of　the　power　delivery　(PD)　adapter,　switching　frequency　increases　and　volume　decreases.　The　EMI　issues　caused　by　magnetic　near-field　coupling　effects　have　become　bottlenecks　in　the　PD　adapter＇s　EMI　suppression.　In　this　paper,　the　coupling　characteristics　of　the　magnetic　field　are　deeply　analyzed,　and　the　equivalent　circuit　considering　near-field　coupling　effects　is　derived.　According　to　the　electromagnetic　field　theory,　the　mathematical　models　of　near-field　coupling　between　transformer　as　well　as　power　PCB　circuits　and　the　input　plug　are　established.　Based　on　this,　the　influence　of　the　structure　parameters　of　the　input　plug　is　studied.　Finally,　a　new　input　plug　loop　structure　is　proposed,　which　can　reduce　the　near-field　coupling　effects　between　the　transformer　as　well　as　power　PCB　circuits　and　input　plug.　The　experimental　results　verify　the　theoretical　analysis　to　be　correct　and　effective.