The ability to predict the influence of dopants (such as antimony) on the shortrange structure of As-S-I glasses has the potential to help design glasses with modified properties. In the present work, the short-range structure of As-Sb-S-I glasses has been investigated along AsSI-SbSI section of fixed sulfur and iodine concentrations and equivalent arsenic by antimony substitution. At high arsenic content (As:Sb≥2:1) antimony substitutes arsenic in AsI3 molecules justified by Raman spectroscopy and XPS. Further antimony introduction (As:Sb<2:1) leads to the substitution of arsenic by antimony in -S-As-S-polymeric chains, leading to SbSI crystallization justified by XRD. The resulting two-dimensional schematic diagrams represent the AsSI-SbSI glasses short-range structure and show the mechanism of arsenic by antimony substitution.