Damaging characteristic of continuous wave (CW) CO2 laser to Ge-Sb-Se chalcogenide glass is studied based on the thermal conduction and experimental study. Studies show that the laser induced damage is mostly damage when heat accumulation causing temperature rising exceeds decomposition temperature of glass. Damage characteristics include meteorite pits, micro-cracks and holes. Se substance is vaporized because of its low melting points, accordingly glass is decomposed in irradiation area. For a Ge-Sb-Se glass of 3 mm thickness, its absorption coefficient is 0.013 cm-1, the sample may be induced damage by a laser irradiation of 74.3 kW/cm2, which is basically consistent with numerical analysis results.