Abstract The molecular orbital calculation has been conducted on Ni-, Fe-, Cr- and Ti-based transition metal alloys using the DV-Xα cluster method. The calculated parameters of the bond order and Md (average energy level of the d-orbital for alloying element) are compared with the experimental partial molar enthalpies of formation of liquid alloys and also with the Miedema's semi-empirical calculation. As a result, it is found that both the parameter Md and the calculated partial molar enthalpies of formation using the Miedema scheme correlate with the experimental partial molar enthalpies of formation. The partial molar enthalpies of formation become larger when there is a larger difference in the number of d-electrons between an alloying element and a base metal. As the ionicity of alloying elements correlates with the Md, charge transfer between an alloying element and a base metal is considered to contribute to the chemical bonding even in the transition-metal-based alloys.