Grain　boundary　diffusion　technique　with　DyH3　nanoparticles　was　applied　to　fabricate　Dy-less　sintered　Nd-Fe-B　permanent　magnets　with　high　coercivity.　The　magnetic　properties　and　microstructure　of　magnets　were　systematically　studied.　The　coercivity　and　remanence　of　grain　boundary　diffusion　magnet　were　improved　by　60%　and　reduced　by　7%　compared　with　those　of　the　original　magnet,　respectively.　Meanwhile,　both　the　remanence　temperature　coefficient　(alpha)　and　the　coercivity　temperature　coefficient　(beta)　of　the　magnets　were　improved　after　diffusion　treatment.　Investigation　shows　that　Dy　is　preferentially　enriched　as　(Nd,　Dy)(2)Fe14B　phase　in　the　surface　region　of　the　Nd2Fe14B　matrix　grains　indicated　by　the　remarkable　enhancement　of　the　magneto-crystalline　anisotropy　field　of　the　magnet.　As　a　result,　the　magnet　diffused　with　a　small　amount　of　Dy　nanoparticles　possesses　enhanced　coercivity　without　remarkably　sacrificing　its　magnetization.