When%20metal%20object%20is%20intruded%20into%20the%20wireless%20power%20trasfer%20system,%20it%20will%20not%20only%20affect%20the%20transmission%20efficiency%20of%20the%20system,%20but%20also%20lead to the%20occurrence%20of%20fire%20and%20other%20safety%20accidents.%20In%20this%20paper,%20an%20active%20detection%20scheme%20for%20metallic%20object%20based%20on%20impedance%20change%20is%20proposed.%20By%20adding%20a%20detection%20coil%20array%20and%20an%20excitation%20source%20on%20the%20surface%20of%20the%20transmitting%20coil%20of%20the%20radio%20energy%20transmission%20system,%20the%20detection%20problem%20is%20solved%20when%20the%20passive%20detection%20scheme%20cannot%20realize%20power%20loss.%20The%20structure%20of%20the%20detection%20coil%20is%20designed,%20compared%20with%20the%20traditional%20detection%20coil%20scheme,%20and%20the%20blind%20spot%20problem%20of%20the%20traditional%20detection%20scheme%20is%20solved.%20The%20selection%20principle%20of%20resonance%20frequency%20in%20the%20detection%20coil%20loop%20is%20discussed,%20and%20the%20deviation%20frequency%20is%20selected to improve%20the%20detection%20sensitivity.%20By%20setting%20up%20the%20finite%20element%20simulation%20model,%20the%20detection%20results%20of%20different%20types%20of%20metal%20foreign%20bodies%20were%20studied.%20The%20experimental%20results%20show%20that%20the%20detection%20scheme%20can%20effectively%20detect%20the%20location%20of%20metal%20foreign%20bodies%20when%20they%20are%20mixed%20with%20the%20radio%20energy%20transmission%20system.