The　effects　of　adding　different　diffusion　medium　(KCl　and　CaCl2)　on　the　regeneration　of　Nd-Fe-B　magnet　sludge　by　CaH2　reduction　diffusion　(RD)　method　were　investigated.　Through　thermodynamic　calculations,　phase-structure　and　microstructure　analysis,　we　found　that　the　liquid　CaCl2　could　lower　the　starting　reaction　temperature　of　the　CaH2-RD　reaction.　And　the　gaseous　KCl　led　to　the　formation　of　loose　and　porous　reacted　compact,　which　was　beneficial　for　impurity　removal　and　refining　the　grains.　Besides,　CaCl2　would　be　involved　in　the　CaH2-RD　reaction　and　produce　the　intermediate　product　NdOCl,　while　KCl　would　not.　Therefore,　the　regenerated　Nd-Fe-B　powders　with　finer　particle　size,　low　impurity　content　and　uniform　particle　size　distribution　were　prepared　when　KCl　was　used　as　diffusion　medium.　The　average　particle　size　of　the　regenerated　Nd–Fe–B　powders　were　reduced　from　3.49　μm　to　1.83　μm.　The　contents　of　Ca　and　O　for　the　regenerated　Nd-Fe-B　powders　were　reduced　to　0.04　wt%　and　0.26　wt%,　respectively.　The　M3T　of　regenerated　Nd-Fe-B　powders　increased　to　152.25　emu/g,　which　was　about　4.1%　and　38%　higher　than　CaH2-regenerated　Nd-Fe-B　powder　and　initial　sludge,　respectively.　Finally,　the　regenerated　Nd-Fe-B　sintered　magnets　with　properties　of　Hcj　=　16.5　kOe,　Br　=　11.7　kG,　and　(BH)m　=　31.8　MGOe　were　successfully　prepared　by　adding　40　wt%　Nd4Fe14B　alloy　powders.　©　2023　Elsevier　B.V.