To　balance　the　utilization　of　rare-earth　resources　and　reduce　the　preparation　cost,　the　La　and　Ce　substituted　Nd2Fe14C　hard　magnetic　alloys　were　prepared　by　a　facile　mechanochemical　method　for　the　first　time.　A　two-step　process　is　typically　employed:　1)　Decomposition　of　hydrocarbon　and　disproportionation　of　(Nd1-xREx)(2.5)Fe14B0.08　(RE=La　or　Ce,　x=0-0.3)　alloys　during　high-energy　ball　milling,　Nd+Nd2Fe17+n-hexane　-＞　NdH2+delta+alpha-Fe+Fe7C3;　2)　(Nd,　RE)(2)Fe14C　hard　magnetic　powders　were　obtained　via　the　vacuum　annealing　at　800　degrees　C　for　2　min.　The　phase　relation,　magnetic　properties　and　microstructural　evolution　of　(Nd,　RE)(2)Fe14B0.08C0.92　(named　Nd-RE-Fe-C-based)　alloys　were　systematically　investigated.　Substitution　of　La　for　x=0.1　Nd　in　the　Nd-RE-Fe-C-based　alloy　increase　the　coercivity　from　15.6　kOe　to　18.6　kOe　without　reducing　the　remanence.　First-principles　calculation　was　performed　to　study　the　mechanism　of　magnetic　properties　La　and　Ce　substituted　samples.　The　results　showed　that　La　tends　to　be　expelled　from　2:14:1　phase　to　form　more　minor　phases　which　act　as　the　domain　wall　pinning　center,　increasing　the　coercivity.　However,　Ce　prefers　to　enter　the　2:14:1　phase,　diminishing　the　permanent　magnetic　properties　due　to　the　poor　intrinsic　magnetic　properties.　This　paper　provides　a　novel　viewpoint　for　the　effective　utilization　of　high　abundant　rare　earth　and　the　investigation　of　low　cost　Nd2Fe14C　permanent　magnet　materials.