A　common　and　urgent　problem　in　electric　vehicle　wireless　charging　technology　is　the　accidental　entry　of　metal　objects　into　the　charging　area　where　there　is　no　direct　physical　contact.　Eddy　currents　can　be　induced　in　the　metal　objects,　generating　a　large　amount　of　heat　and　potentially　leading　to　serious　consequences　such　as　fire.　The　current　commercially　applied　metal　object　detection　technology　has　the　problems　of　low　detection　sensitivity,　affecting　the　power　transmission　magnetic　field,　and　the　existence　of　blind　zones.　In　view　of　these　shortcomings,　a　metal　object　detection　system　for　wireless　charging　of　electric　vehicles　is　proposed　in　this　paper.　Long　strip　detection　coils　are　designed　and　placed　above　the　transmitter　coil.　Each　strip　detection　coil　is　composed　of　16　unipolar　coils　having　alternating　polarities,　which　can　realize　decoupling　between　the　detection　coil　and　the　transmitter　coil　and　eliminate　the　interference　to　the　magnetic　field　of　the　wireless　power　transmission　system.　A　third-order　Sallen-Key　high　pass　filter　and　a　proportional　amplifier　circuit　are　used　to　improve　the　sensitivity　and　accuracy　of　metal　object　detection.　Finally,　an　experimental　platform　of　metal　object　detection　for　electric　vehicle　wireless　charging　is　built,　and　the　proposed　system　can　detect　the　existence　of　metal　objects　sensitively　and　accurately　at　the　location　where　they　may　exist.　©　2015　IEEE.