A　novel　Nd-Fe-B　based　permanent　magnets　named　as　SPSed　NdFeB　magnets　were　prepared　by　spark　plasma　sintering　(SPS)　technique.　In　order　to　better　comprehend　the　mechanism　of　the　changes　in　magnetic　properties　of　the　SPSed　NdFeB　magnets　treated　in　an　optimized　process,　the　effects　of　the　heat　treatment　process　on　the　microstructure　of　magnets　were　systematically　studied　by　scanning　electron　microscopy　(SEM),　energy　dispersive　X-ray　spectroscopy　(EDXS),　high-resolution　transmission　electron　microscopy　(HRTEM),　respectively.　The　results　show　that　the　increase　in　coercivity　of　the　magnet　is　related　to　the　obvious　decrease　in　ratio　of　Fe　to　RE　(Fe/Re)　in　Re-rich　phase,　and　the　RE-rich　phase　transforms　to　crystalline　state　from　amorphous　state　after　heat　treatment　process.