Abstract: Electro-optical detectors are widely used in many fields. However, temperature rise due to the absorption of laser and other phenomena may damage detectors. Using thermal elastic theory, the investigation on K9 material radiated by CO2 laser is done. According to the two-dimensional planar model, the transient distributions of temperature field and thermal stress field which result from laser radiation on semiconductor material are obtained by analytical calculation. The results show that the K9 glass damage threshold of laser radiation is dependent on the radiation time and beam radius. Under the same conditions, the thermal stress damage threshold is lower than the melting damage threshold, so the damage reason of K9 glass material is thermal stress damage.