Waste　sintered　Nd-Fe-B　permanent　magnets　were　recycled　via　NdH　nano-particle　doping　method.　Effect　of　the　NdH　nano-particle　content　on　the　microstructure　and　magnetic　properties　of　the　recycled　magnets　has　been　studied.　As　the　NdH　nano-particle　content　increases,　the　coercivity　(Hcj)　increases　from　926.54　kA/m　to　1299.87　kA/m.　The　remanence　(Br)　of　about　1.296　T　keeps　unchanged　and　then　decreases　until　additive　exceeds　2.0wt%.　Compared　to　the　properties　of　the　starting　scrap　sintered　magnet,　97.58%,　95.9%,　89.7%　of　Hcj,　Br　and　(BH)max　have　been　recovered　in　the　recycled　magnets　with　2.0wt%　NdH　nano-particles　additive,　respectively.　Through　calculation,　the　volume　of　Nd-rich　phase　increases　as　NdH　nano-particle　content　increases,　and　reaches　its　maximum　of　5.7　vol%　for　3.0　vol%　additive.　However,　grain　size　of　the　recycled　magnets　with　3.0　wt%　additive　grow　up　to　11.68　μm　from　8.18　μm.　It　was,　therefore,　concluded　that　2.0wt%　NdH　nano-particle　additive　was　the　best　content　for　recovering　the　properties　of　the　waste　magnets.