The physicochemical, optical, and luminescent properties and structures of glasses of the Ga 2S 3-GeS 2-Sb 2S 3:Pr system have been studied in a wide range of concentrations of the main components in order to reveal their correlation with the composition. According to the calculations using the Judd-Ofelt theory, glasses with a high content of Sb 2S 3 should provide the highest luminescence efficiency of Pr 3+ ions. However, this result is leveled by enhancing the concentration quenching effect, followed by an increase of the Sb 2S 3 content in the glasses. The introduction of Pr leads to a significant increase in the fraction of Sb-Sb, Sb-Ge, Ge-Ge bonds in glasses enriched with Sb 2S 3 and GeS 2. In the cases of the glasses enriched with Ga 2S 3, this effect was not observed, apparently because Ga promotes the formation of three-coordinated sulfur atoms.