The influences of surface impurities, etching time, subsurface defects and the width to depth ratio on the laser damage threshold of fused silica optics in the traditional grinding and polishing process are systematically analyzed by laser damage experiments. Results show that the laser damage thresholds are 21.6 J/cm2 and 11.28 J/cm2 for wiped and non-wiped optics, respectively. The laser damage threshold is greatly reduced by the surface impurities, while the laser damage threshold at the defect area is significantly lower than that at no defect area. The increase of the etching time increases the surface roughness and defect size of the workpiece, which leads to a significant decrease in the laser damage threshold of the optics, so a reasonable choice of chemical etching time is required. The incident light field can be modulated by subsurface defects, resulting in local area reflected light, scattered light and incident light superimposed on each other, eventually leading to laser damage of optical material. The width to depth ratio of the scratch increases with the etching time, which can gradually weaken the scratch on the light field modulation, thereby the probability of occurrence of laser damage for fused silica optics is reduced.