Melt　spun　ribbons　of　Nd4.5Fe77B18.5　alloy　were　consolidated　into　bulk　permanent　magnets　by　spark　plasma　sintering　(SPS)　method.　Effects　of　heat　treatment　on　the　density,　microstructure　and　magnetic　properties　of　the　magnets　are　studied.　Further　observation　shows　that　the　sample　consolidated　by　SPS　possesses　ultrafine　nanocrystalline　structure　and　small　fraction　of　amorphous　phase.　After　proper　heat　treatment,　magnets　with　fine　crystal　structure　and　good　magnetic　properties　were　obtained　simultaneously.　On　the　other　hand,　excessive　grains　growth,　which　will　lead　to　undesirable　magnetic　properties,　can　occur　due　to　improper　heat　treatment.