The absorption and emission spectra of chalcogenide glasses (Ga-La-S:O) doped with trivalent Praseodymium were experimentally investigated and theoretically discussed. The glasses show bright luminescence due to Pr ³⁺ ion emission. The effect of oxygen on the luminescence spectra is determined by decreasing of host glass self-absorption of the shortwavelength bands. In order to obtain the good agreement between the theoretical model and experimental results we apply the Judd-Ofelt theory for this glass matrix. Radiative transition rates are calculated and compared with measured experimental parameters. The radiative and non-radiative transition processes between the energy levels of the Pr³⁺ ions stimulated by optical and acoustical vibration modes are proposed in order to obtain the quantitative correlation between the proposed theoretical model and experimental results.