It has very important application value to investigate the damage performance of K9 glass irradiated by ultraviolet excimer laser. In this paper, the experiment research on damage in K9 glass irradiated by 248 nm KrF excimer laser was carried out, the sample damage threshold and damage morphology were analyzed by means of metallurgical microscope and scanning electron microscope. The comparison of laser induced damage performance between KrF excimer laser and pulse CO2 laser were investigated. The experimental results indicate that the damage mechanism of K9 glass irradiated by KrF excimer laser and pulse CO2 laser mainly follow the thermal-mechanical coupling mechanism. However, there is apparent difference in damage threshold and damage time. For example, the damage threshold is lower and the damage time is shorter for KrF excimer laser. This can be explained by the difference in wavelength and photon energy between the KrF excimer laser and pulse CO2 laser. The research presented in this paper is helpful for further exploring the ultraviolet excimer laser damage mechanism of optical materials.