Many　consumer　electronics　employ　wireless　charging　technology,　but　it　is　difficult　to　achieve　free　positioning　wireless　charging.　Also,　significant　changes　in　the　mutual　inductance　can　happen　when　moving　the　device　during　charging,　causing　hazards　to　the　devices.　This　paper　proposes　a　solenoid　coil　that　solves　this　problem　by　utilizing　reverse　windings　to　maximize　average　mutual　inductance　and　stabilizing　its　variance.　Firstly,　the　design　principle　of　the　reverse　winding　is　explained,　and　then　the　flow　chart　of　the　optimal　design　is　given.　The　optimal　layer　number　of　the　outer　winding　of　the　solenoid　is　determined,　and　the　reverse　winding　is　placed　in　the　innermost　layer.　The　maximum　average　mutual　inductance　obtained　under　the　condition　of　a　limited　mutual　inductance　fluctuation　ratio　is　13.866　mu　H　.　Compared　with　the　results　without　the　reverse　winding,　the　mutual　inductance　fluctuation　is　reduced　by　nearly　2　times.　In　addition,　placing　the　solenoid　coils　on　the　transmitter　side　in　a　hexagonal　shape　enables　the　receiver　to　cover　a　larger　transmission　area　during　movement.　Finally,　a　low-power　experimental　prototype　is　designed,　and　the　experimental　results　verify　the　effectiveness　of　the　design　method.