Various processes of non-radiative energy transfer between erbium ions in Ga-Ge-S:Er³⁺ chalcogenide glasses using the time-resolved luminescence spectroscopy are considered. The evaluation of the energy transfer constants C_SA and C_SS for the ⁴I_9/2, ⁴F_9/2 and ⁴S_3/2 Er³⁺ levels is presented. The variation of the studied glasses structure with an increase of erbium ions concentration is shown by means of estimation of the minimum distance between Er³⁺ ions as permitted by the glass matrix (R_min).