Circular　planar　spiral　coils　are　wildly　used　for　the　magnetic　coupling　system　in　a　high-frequency　wireless　power　transfer　system.　The　loss　of　the　magnetic　coupling　system　usually　takes　dominance　in　the　whole　system.　This　paper　built　the　calculation　model　of　magnetic　field　strength　and　coil　loss,　the　proposed　calculation　model　can　effectively　consider　the　mutual　influence　between　the　transmitter　and　receiver　coil　and　accurately　calculated　the　AC　loss　of　WPT　coils.　Then,　the　effect　of　turn　spacing　on　the　AC　resistance　of　coil　is　analyzed.　It　reveals　that　the　proximity　effect　loss　is　greater　when　the　coil　is　tightly　wound,　and　the　AC　loss　can　be　optimized　by　designing　the　turn　spacing.　Based　on　the　above　analysis,　a　double-layer　coil　method　is　proposed.　This　method　can　reduce　the　AC　loss　and　improve　the　quality　factor　(Q)　without　changing　the　mutual　inductance　and　footprint　of　coil　at　high　frequency.　The　AC　resistance　of　the　double-layer　coil　method　can　be　greatly　reduced　compared　with　the　general　method　through　simulation　and　experiment.　The　work　efficiency　of　WPT　system　is　increased　by　4.3%,　which　verifies　the　accuracy　and　flexibility　of　theoretical　analysis.