The　carbide　precipitation　behavior　of　35　wt%Cr-4　wt%C　(35Cr-4C)　Hypereutectic　High　Chromium　Cast　Iron　(HHCCI)　during　heat　treatment　was　investigated　by　means　of　scanning　electron　microscope　and　transmission　electron　microscope,　and　the　effect　of　rare　earth　magnesium　(RE-Mg)　modification　on　the　microstructure　evolution　and　wear　resistance　of　35Cr-4C　cast　iron　was　also　studied.　The　as-cast　structure　of　35Cr-4C　HHCCI　is　mainly　composed　of　primary　carbides,　eutectic　carbides　and　austenite　matrix.　After　quenching,　there　are　secondary　carbides　M7C3　and　M23C6　precipitation　in　the　martensite　matrix.　After　tempering,　more　secondary　carbides　will　be　formed　and　the　main　precipitate　phase　is　M23C6.　After　heat　treatment　of　RE-Mg　modified　HHCCI,　more　secondary　carbides　are　precipitated,　and　the　distribution　in　the　matrix　is　more　uniform,　and　the　wear　resistance　is　higher　than　that　of　unmodified　HHCCI.