The　intermetallic　compounds　based　on　the　tetragonal　ThMn12　prototype　crystal　structure　have　exhibited　great　potential　as　advanced　rare-earth-lean　permanent　magnets　due　to　their　excellent　intrinsic　magnetic　properties.　However,　the　trade-off　between　the　phase　stability　and　the　magnetic　performance　is　often　encountered　in　the　ThMn12-type　magnets.　This　work　was　focused　on　the　effects　of　V　doping　and　nanostructuring　on　the　phase　stability　and　magnetic　properties　of　ThMn12-type　Sm-Co-based　magnets.　Novel　SmCo12-based　nanocrystalline　alloys　with　the　SmCo12　main　phase　were　prepared　for　the　first　time.　The　prepared　alloys　from　the　optimal　design　achieved　obviously　higher　coercivity　than　the　isotropic　SmFe12-based　alloys,　together　with　comparable　performance　of　other　magnetic　features.　The　enhancement　in　the　coercivity　was　ascribed　to　the　pinning　of　domain　walls　by　the　nanocrystalline　grain　boundaries　and　stacking　faults.　First-principles　calculations　and　magnetic　structure　analysis　disclosed　that　V　substitution　can　stabilize　the　SmCo12　lattice　and　elevate　its　magnetocrystalline　anisotropy.　This　study　provides　a　new　approach　to　developing　stabilized　metastable　structured　rare-earth-lean　alloys　with　high　magnetic　performance.　©　2024