The electronic structure of high Ni-Co secondary hardening martensitic steel has been investigated by the recursion method in the tight-binding approximation. The local density of states(LDOS) of alloying elements in two kinds of structure (with carbon or without carbon) have been caculated. By the integration of the total density of states(TDOS), the Fermi energy of system, the bond order integral(BOI) between atoms are presented for alloying steel. On the basis of these results, the bonding characteristics, the physical properties as well as the influence of different alloying elements on physical properties of high Ni-Co secondary hardening martensitic steel are discussed.