The　coupled　magnetic　resonant　unit　(CMRU)　has　great　effect　on　the　transmitting　power　capability　and　efficiency　of　magnetic　resonant　wireless　power　transfer　system.　The　key　objective　i.e.　the　efficiency　coefficient　kQ　is　introduced　in　the　design　of　CMRU　or　the　coupled　windings　based　on　the　mutual　inductance　model.　Then　the　design　method　with　orthogonal　experiments　and　finite　element　method　simulation　is　proposed　to　maximize　the　kQ　due　to　low　precise　analytical　model　of　AC　resistance　and　inductance　for　PCB　windings　at　high-frequency.　The　method　can　reduce　the　design　iterations　and　thereby　can　get　more　optimal　design　results.　The　experiments　verified　the　design　objective　of　kQ　as　well　as　the　design　method　effectively.　In　the　optimal　PCB　windings　prototype　at　operating　frequency　of　4　MHz,　the　kQ　and　the　maximum　efficiency　are　increased　by　about　12　%　and　4　%　respectively.