This　letter　proposed　a　novel　high-current　planar　inductor　with　cooling　fins　based　on　3-D　printing　and　its　copper　winding　is　3-D　printed　by　using　selective　laser　melting　technology.　The　3-D-printed　winding　is　designed　for　high-current　applications　based　on　3-D　space　and　can　work　as　both　winding　and　cooling　fins.　Compared　with　conventional　printed　circuit　board　(PCB)　planar　inductor,　the　proposed　planar　inductor　not　only　has　better　performance,　such　as　low　dc　resistance　(DCR),　ac　resistance,　and　temperature　rise,　without　volume　increasing,　but　also　has　the　superiorities　of　conventional　PCB　planar　magnetics,　such　as　ease　of　manufacture　and　controllability.　To　verify　its　performance,　a　100-A-output　buck　converter　using　the　proposed　inductor　was　fabricated　and　compared　with　another　identical　buck　converter　using　a　conventional　PCB　inductor　with　the　same　size.　The　DCR　of　the　proposed　inductor　is　almost　one-fifth　of　the　PCB　inductor.　Besides,　the　efficiency　of　the　buck　converter　with　the　proposed　inductor　is　always　over　0.5%　higher　than　that　with　PCB　inductor　under　different　loads　and　its　maximum　efficiency　is　nearly　1%　higher　at　light　load.　Furthermore,　the　maximum　temperature　rise　of　the　proposed　inductor　is　26.8　degrees　C　under　full　load,　only　one-third　of　the　PCB　planar　inductor.　In　other　words,　the　proposed　inductor　can　work　well　under　100-A　current,　whereas　the　traditional　PCB　inductor　cannot　due　to　too　high　temperature　(103.8　degrees　C).