In the present paper we have focused our study on relaxation of photodarkening in α-As S doped with rare-earth ions (Dy , Pr , Nd ). It was shown that the degree of photo- structural transformation depends on the species and concentration of rare-earth ions. The relaxation process of photodarkening is described by a stretched exponential function with the dispersion parameter 0<α<1.0. The obtained results can be taken into account for chalcogenide glasses doped with rare-earth ions used as fiber optics amplifiers operating at the 1.3 μm and 1.5 μm telecommunication windows.