Nutation　reducers　have　recently　attracted　increasing　attention,　as　they　are　used　in　important　components　of　industrial　robot　joints.　A　novel　disk-type　nutation　magnetic　drive　(NMD),　based　on　the　nutation　gearing　principle,　is　proposed　in　this　article.　Subsequently,　a　3-D　method　for　analyzing　the　magnetic　field　and　predicting　the　torque　of　the　disk-type　NMD　is　presented.　The　3-D　analytical　formula　of　the　disk-type　NMD　is　established　on　the　basis　of　the　equivalent　current　theory　of　permanent　magnet,　which　is　verified　by　the　finite-element　approach.　Optimization　design　of　the　disk-type　NMD　is　also　carried　out　by　applying　the　genetic　algorithm.　The　results　provide　a　reference　for　the　design　and　optimization　of　the　magnetic　gears.　©　1965-2012　IEEE.