Grain　boundary　diffusion　technique　with　TbH3　nanoparticles　was　applied　to　fabricate　Tb-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　are　improved　by　112　%　and　reduced　by　26　%　compared　with　those　of　the　original　magnet,　respectively.　Meanwhile,　both　the　remanence　temperature　coefficient　(alpha)　and　the　coercivity　temperature　coefficient　(beta)　of　the　magnets　are　improved　after　diffusion　treatment.　Microstructure　shows　that　Tb　element　enriches　in　the　surface　region　of　Nd2Fe14B　grains　and　is　expected　to　exist　as　(Nd,Tb)(2)Fe14B　phase.　Thus,　the　magneto-crystalline　anisotropy　field　of　the　magnet　improves　remarkably.　As　a　result,　the　sintered　Nd-Fe-B　magnets　by　grain　boundary　diffusion　with　TbH3　nanoparticles　exhibit　enhanced　coercivity.