In　this　work,　we　explore　how　Ce　in　(Nd,　Ce)-Fe-B　magnet　optimizes　the　microstructure　of　the　base　magnet,　and　enhances　Grain　Boundary　Diffusion　(GBD)　of　Dy.　As　Ce/total　rare　earth　(TRE)　content　increases　from　0　wt%　to　16.95　wt%,the　coercivity　of　the　base　magnets　decreased　by　24.93　%.　However,　lower-melting-point　Ce　element　tended　to　distribute　in　the　grain　boundaries　(GBs),　and　the　thickness　of　the　GBs　layer　increased　from　2.46　nm　to　5.54　nm.　This　provided　more　pathways　for　the　subsequent　GBD.　Importantly,　the　diffusion　depth　of　Dy　element　increased,　and　more　core-shell　structure　formed　as　Ce　increased.　It　led　to　a　higher　coercivity　increment.　Compared　to　GBD　magnets　without　Ce,　the　coercivity　increment　of　GBD　magnets　with　Ce/TRE　=　16.95　wt%　increased　by　39.54　%.