Structure　and　magnetic　properties　were　studied　for　bulk　nanocrystalline　isotropic　and　anisotropic　Nd-Fe-B　permanent　magnets　prepared　by　spark　plasma　sintering　(SPS).　The　neck　formation　among　the　Nd-Fe-B　powders,　which　was　governed　by　sintering　conditions　in　the　SPS　process,　has　a　substantial　influence　on　the　microstructure　and　subsequent　magnetic　properties　of　the　magnets.　By　tuning　the　current　pulse　ratio　of　power-on　to　power-off　time　during　sintering　from　12:　2　to　2:　2,　we　successfully　reduced　the　thickness　of　the　surface　diffusion　layer　of　the　Nd-Fe-B　particles　in　both　hot-pressed　and　hot-deformed　magnets.　As　a　result,　the　maximum　energy　product　(BH)　max　of　the　isotropic　and　anisotropic　magnets　increases　by　27%　and　9%,　respectively.