Glass formation tendency has been studied for five different compositions of the Snx-Sb15-Se85-x system, where x 0, 5, 10, 12.5, and 15-mole . Melt quench-synthesised samples have been characterised using a variety of experimental techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, differential thermal analysis (DTA), and density measurement. The XRD analysis for x 0 up to 12.5-mole gave an indication of amorphous phase, while for x 15-mole , it showed a tendency of crystalline structure. The results obtained from FTIR showed a shift in IR-peak intensities and widths from the long to the short wavelengths upon the addition of Sn-mole . This change implied the breaking of Se-chains that appeared around 208-250 cm-1 as well as the occurrence of pyramidal SbSe3 and asymmetrical tetrahedral SnSe4 modes around 176-208 cm-1and 125-145 cm-1, respectively. In addition, Raman spectra revealed a pyramidal SbSe3 peak located at 190 cm-1. The intensity of this peak increased and shifted to 183 cm-1 when Sn-mole was added to the system. Differential thermal analysis revealed that the glass transition temperature decreased with an increase of Sn-mole . The results confirmed the validity of using 4, 3, and 2 co-ordination numbers of Sn, Sb, and Se, respectively, in the amorphous samples.