Although　HfB12　is　a　promising　surperhard　material　because　of　the　boron　cuboctahedron　cage,　the　Vickers　hardness　of　HfB12　remains　controversial.　We　apply　first-principles　calculations　to　investigate　the　influence　of　a　transition　metal　on　the　structural　stability,　Vickers　hardness　and　thermodynamic　properties　of　HfB12.　The　Vickers　hardness　of　HfB12　is　39.3　GPa.　In　particular,　the　Vickers　hardness　of　TM-doped　HfB12,　which　are　novel　superhard　materials,　is　larger　than　40　GPa.　The　Vickers　hardness　of　Re-doped　HfB12　is　up　to　47.6　GPa.　The　improvement　of　Vickers　hardness　is　that　the　introduction　of　an　alloying　element　improves　the　localized　hybridization　between　B　and　Hf,　and　then　enhances　the　bond　strength　of　the　B-B　covalent　bond　and　the　Hf-B　bond.　In　addition,　these　alloying　elements　enhance　the　melting-point　and　Debye　temperature　of　the　HfB12.　Therefore,　we　believe　that　alloying　is　an　effective　method　to　improve　the　Vickers　hardness　and　thermodynamic　properties　of　HfB12　superhard　material.