Circular　planar　coil　is　one　of　the　most　popular　structures　in　wireless　charger　for　electric　vehicles　and　portable　devices.　A　methodology　of　transmitting　coil　design　to　achieve　the　uniform　distribution　of　axial　magnetic　field　strength　on　the　charging　plane　where　the　receiving　coils　placed　was　proposed.　The　coil　structure　design　was　regarded　as　a　parametric　optimization　problem　and　solved　by　Adaptive　Genetic　Algorithm　(AGA).　Some　design　examples　were　performed　and　simulated　by　Finite　Element　Method　(FEM).　A　transmitting　coil　of　15　turns　was　made　and　the　field　was　measured　to　verify　the　design　results.　The　multi　receiving　coils　were　also　made　to　test　the　feature　of　constant　mutual　inductance.