Under the framework of second moment approximation of the tight binding theory, a realistic interatomic potential is first developed for the Ni-Zr-Al ternary metal system and then applied to predict the glass-forming ability of the system through molecular dynamics simulation. It is found that when the composition falls into the hexagonal region defined by six vertexes of Ni Al 0 , the super-saturated solid solution becomes unstable and spontaneously turns into the disorder state, i.e., the metallic glass state. The defined composition region could be considered as a quantitative glass-forming ability, within which the Ni-ZrAl ternary metallic glass is predicted to be energetically favored to form. Interestingly, the prediction based on the interatomic potential matches well with experimental observations.