Laser damage performance of large aperture optical components has been study under fourth harmonic of 1053nm Nd:glass laser irradiation (263nm).The threshold of optical components is very low under 263nm laser irradiation ,due to conversion of beam to higher energy photons of the quadrupled frequency (4ω), and is relative to material characteristic. A preliminary test of laser induced damage in fused silica (SiO2) and CaF2under 263nm laser is reported in this article. Thresholds of these two materials are obtained. Laser damage threshold of SiO2 is found about 2 J/cm2 by 1-on-1 method using pulsed 263nm laser, lower than CaF2 whose threshold.