This paper studied systematically the physical and acousto-optic properties for Ge-As-S glass system. Experimental results show that the density, hardness, softening temperature, chemical durability etc. of these glasses increase with Ge contents in glasses. The thermal expansion coefficient of the glasses decreases with Ge contents in glasses. The fundamental absorption edge of the glasses shifts to longer wavelengths. Meanwhile, the acoustic attenuation of the glasses decreases with increasing Ge contents. The acoustic attenuation of glasses of the system is as small as quartz glass. When Ge(30)As(15)S(55) glass sample was used to carry out the experiment outside the laser cavity, diffraction effect of four or five grades was observed. However there isn't suoh a phenomenon in tbo same size quartz glass sample. So Ge-As-S glass system has excellent aoousto-optio properties. It is a prospective infrared aeousto-optio modulation material.