TbHx　nanoparticles　were　applied　to　prepare　sintered　MM-Fe-B　magnet　by　using　grain　boundary　diffusion　technique.　Under　optimal　processing　conditions,　the　coercivity　and　maximum　energy　product　substantially　increase　by　383%　and　151%,　reaching　to　6.81　kOe　and　20.18　MGOe,　respectively.　Further　investigation　indicates　that　the　interchange　between　Tb　atoms　and　Ce　atoms　leads　to　a　core/shell　structure　with　(MM,Tb)(2)Fe14B　phase　in　the　surface　region　of　MM2Fe14B　matrix　grains　in　the　magnet.　The　modified　structure　successfully　restrains　the　magnetic　domain　reversal　process,　resulting　in　remarkable　enhancement　of　coercivity　and　maximum　energy　product　of　the　magnet.