The　origin　of　low　coercivity　of　high　La-Ce-containing　Nd-Fe-B　sintered　magnets　was　analyzed　based　on　characterization　of　the　microstructure,　magnetic　domain　structure,　and　magnetization　reversal　process.　It　can　be　found　that　the　coercivity　of　magnet　decreases　sharply　and　the　ratio　value　of　coercivity　(H-cj)　to　anisotropic　field　(H-A)　is　below　the　theoretical　value　when　the　amount　of　La-Ce　substitution　for　Nd　is　more　than　40　wt%.　The　grain　boundaries　with　poor　magnetic　isolation　in　the　high　La-Ce-containing　Nd-Fe-B　sintered　magnets　play　an　important　role　in　reducing　the　coercivity　of　the　magnet.　In　addition,　a　larger　proportion　of　the　reversible　portions　can　be　found　for　the　magnet　with　a　large　content　of　La-Ce,　which　will　lead　to　the　low　performance　of　the　magnet.　Graphic　abstract