Glass samples of the Ge–Sb–Se–I system were prepared by reacting germanium tetraiodide and antimony triiodide with selenium in a set-up which provides selective removal of iodine from the melt. Thermodynamic modeling of purification reactions of the components is shown. The glasses are analyzed by X-ray spectral microanalysis, differential scanning calorimetry, IR spectroscopy, Raman scattering spectroscopy, and laser mass spectrometry. In the purest examples of these glasses, the content of residual impurities is: hydrogen—0.1ppmmol, silicon—0.02ppmwt., and transition metals—less than 0.5ppmwt. •A new method for preparation of Ge–Sb–Se–I glasses has been developed.•Thermodynamic modeling of heterogeneous equilibrium in GeI4–Se system was performed.•The produced Ge–Sb–Se–I glasses are characterized by low content of impurities.