In　this　work,　efficient　grain　boundary　diffusion　(GBD)　of　Tb　can　be　achieved　in　fine-grained　sintered　Nd-Fe-B　magnet　through　the　addition　of　Zr.　The　magnets　were　prepared　using　Nd-Fe-B　powder　with　an　average　particle　size　of　2.6　μm.　Compared　with　the　magnet　without　Zr　addition,　the　intrinsic　coercivity　of　the　Zr-added　magnet　increases　by　3.55　kOe　after　GBD　with　the　increment　of　15.0　%,　and　the　squareness　of　the　demagnetization　curve　is　improved　by　5.7　%.　The　Zr　element　can　combine　with　the　C　element　in　the　magnet　to　form　block-like　ZrC　precipitates,　which　inhibits　the　formation　of　harmful　rare-earth　carbon　phase　and　reduces　the　ineffective　depletion　of　rare　earth　elements.　In　addition,　the　Zr　element　can　also　combine　with　the　B　element　to　form　needle-like　ZrB2　precipitates.　The　consumption　of　B　element　increases　the　volume　fraction　of　RE-rich　phase,　thus　providing　more　liquid-phase　channels　for　the　diffusion　of　Tb.　The　ZrC　and　ZrB2　precipitates　distributed　at　the　grain　boundary　(GB)　can　broaden　the　width　of　the　GB　phase,　which　not　only　provide　broader　channels　for　Tb　diffusion,　but　also　improve　the　magnetic　isolation　of　the　main　phase　grains.　By　the　addition　of　Zr,　the　diffusion　depth　of　Tb　in　the　magnet　is　increased.　Meanwhile,　the　accumulation　of　Tb　on　the　diffusion　surface　of　the　magnet　reduces　significantly,　and　the　thin　and　uniform　Tb-rich　shell　is　formed　on　the　exterior　of　the　main　phase　grains　in　the　magnet.　©　2025　Elsevier　Inc.