Boundaries of glassformation in the system As2S3–Pr6O11 were studied using methods of physico-chemical analysis (X-ray analysis, Raman spectra, Scanning electron microscope). It was established that in glassformation region the range of concentration covers from As2S3–Pr6O11 it is 13 mol%. Samples in the region of glassformation are stable at 300 K to air, water and organic solvents. Samples decompose in mineral acids and alkalies. In the region of glassformation at a temperature of 300 K were studied samples of density and microhardness.