Optical transition properties of Er3+ ions in ZnCl2-KCl-BaCl2 glass were studied and were discussed on the comparison with those in the other glass systems, i.e., ZrF4-based and Ga2S3-based glasses. Judd-Ofelt analysis was performed using eight absorption bands of Er3+ in the ZnCl2-based glass. Among the Judd- Ofelt intensity parameters, the (Omega) 2 was larger than that of the ZrF4-based glass. This is probably due to the covalency of the bonds of the rare-earth and ligand ions in comparison with those of the ZrF4-based glass. Decay curves of the emission from the 4F5/2, 4F7/2, 4S3/2, and 4F9/2 levels were measured. From the lifetime data and the radiative transition probabilities calculated using the Judd-Ofelt intensity parameters, multiphonon relaxation rates are estimated for the four excited levels. The multiphonon relaxation rates of the 4F5/2, 4F7/2, and 4F9/2 were much smaller than those in the ZrF4- based and Ga2S3-based glasses. This is the consequence of the extremely low-phonon-energy property of the ZnCl2-based glass. The multiphonon relaxation rates were inversely proportional to the exponential of the energy gap between the emission and the next-lower levels (a so- called `energy-gap low') as well as the other glass systems.