This study aims to analyze the relationship between the valence electron structure of Fe-N intermetallic compounds in ionic nitriding layers and the performance of the layer. The 45 steel was used as the research object and the hardness, thickness of nitrided layer, phase composition, friction and wear properties, corrosion resistance, and mechanical properties were teseted after ion nitriding. Based on the XRD results and EET theory, the valence electron structure, bond energy and bond energy of Fe-N intermetallic compound phase in the infiltrated layer were calculated, and the relationship of properties and valence electron structure were anlysized. The experimental results show that when the nitriding temperature was 520 ℃ and the nitrogen hydrogen flow ratio was 3∶1, the hardness, wear resistance and corrosion resistance of the nitrided layer were highest, but the brittleness was also the highest, and the impact absorption energy was reduced to 26% of the base metal. The calculation results indicated that covalent electron density of α-Fe, Fe4N, Fe3N and Fe2N were 299.13, 367.68, 416.45, 458.78 nm–3, crystal aerage bonding energies were 412.65, 444.02, 472.48, 486.61 kJ/mol. Covalent electron density of α-Fe, Fe4N, Fe3N and Fe2N were 133.36, 108.58, 84.72, 81.74 nm–3, crystal plasticity factor were 76.20, 14.75, 3.66, 3.65. Under the experimental conditions, the ε has the greatest influence on the plastic toughness of the nitrided layer, the content of ε phase could be effectively reduced by properly reducing the plasma nitriding temperature and nitrogen hydrogen flow ratio to improve the mechanical properties of nitriding parts.