A novel series of Ge20-xTe65Se15Snx(x=0,2,4) chalcogenide glasses is prepared by traditional melt-quenching method. Infrared thermal (8~12 μm) image, X-ray diffraction (XRD), differential scanning calorimetry (DSC), visible/near-infrared absorption spectroscopy and infrared transmission spectra are adopted to analyze the composition, structure and performance of the Ge-Te-Se glasses system with addition of Sn. The Tauc equation is used to calculate the direct and indirect optical band gap. Based on the metallization criterion and band gap energy theory, the relation between optical band gap and composition is investigated. The results show that Ge-Te-Se-Sn glasses have good thermal stability. With the addition of Sn, the optical band gap of glass samples decreases, the short-wavelength edges shift to a longer wavelength, and the infrared cut-off wavelength almost keeps unchanged. Sn can weaken the intensity of the Ge-O absorption peak and improve the infrared transmission properties of glass samples.