The spectroscopic characteristics of chalcogenide glasses in the Ga-Ge-S: Er³⁺ system are determined. The oscillator strengths, the Judd-Ofelt intensity parameters, the probabilities of spontaneous radiative transitions, and the radiative lifetimes of levels are calculated from the absorption spectroscopy data for two series of Ga-Ge-S chalcogenide glasses doped with Er³⁺ ions. In the first series, the Er₂S₃ content is varied from 0.49 to 4.64 mol % at the fixed composition of the glass matrix (0.15Ga₂S₃ • 0.85GeS₂). In the second series, the Ga₂S₃ content is varied from 10 to 30 mol % at the fixed Er₂S₃ content (1.94 mol %). The aforementioned spectroscopic parameters are analyzed as a function of the chalcogenide glass composition. It is revealed that the values of the oscillator strengths and the probabilities of spontaneous radiative transitions in Er ³⁺ ions in the chalcogenide matrix are larger than those in phosphate, germanate, and tellurite matrices.