A traditional melt-quenching method was adopted to prepare a series of (Ge15Ga10Te75)100－x(Ag)x chalcogenide glass samples. The thermal and optical parameters were measured by X-ray diffraction,differential scanning calorimetry and Fourier transform infrared spectroscopy,etc. The results show that these glasses have well amorphous nature and good thermal stability. The differences between the glass onset crystallization temperature and the glass transition temperature are all beyond 100℃. With the addition of silver,the absorption cut-off edge has a red shift. The Ge-Ga-Te-Ag glasses have wide and flat infrared optical windows between 1.8 and 20 μm after a purification method. Therefore,all these properties indicate that Ge-Ga-Te-Ag glasses are potential candidate for far infrared applications.