Effect of As to Sb substitution on glass-forming ability of As2Se3 glass under Ga additions was comprehensively studied using optical spectroscopy in visible and IR regions, differential scanning calorimetry, X-ray diffraction as well as Raman scattering techniques. The crystallization processes enhanced by Ga additions to As2Se3 glass were significantly suppressed under such As to Sb substitution. Following conventional synthesis, it was possible to substitute up to 50% of As by Sb within Ga-y(As0.40-xSbxSe0.60)(100-y) cut-section without essential impact on glassy state, thus improving optical properties in the IR region by lowering the phonon energy. In the case of Ga-y(As0.28Sb0.12Se0.60)(100-y) cut-section, up to 8at.% of Ga can be introduced without crystallization, whereasin case of Ga-y(As0.40Se0.60)(100-y) system, glass-forming ability is limited just up to 3at.% of Ga. The prepared Ga-5(As0.28Sb0.12Se0.60)(95) glass composition was shown to be the richest in Ga keeping its vitreous state, good optical and thermodynamic properties allowing further rare-earth doping and fiber drawing.