Abstract: When surface defects are present on fused silica optical components, they modulate the incident laser field, resulting in a non-uniform internal light distribution with local intensity enhancement. To investigate the laser-field-induced damage mechanisms of optical components, in this study, a finite-difference time-domain (FDTD) model is developed to investigate laser-field-induced damage in fused silica containing surface scratches. By analyzing how the number of scratches, their geometric parameters, and their spacing affect the light-field distribution and damage characteristics, the influence of these factors on the laser-damage resistance of fused silica is investigated. The results indicate that, under fixed incident conditions, increasing the number of scratches enhances light-field modulation and reduces the damage resistance of fused silica. For a single scratch, a smaller width-to-depth ratio leads to a lower damage threshold. With increasing scratch spacing, the light-intensity enhancement first increases and then decreases, while the damage threshold shows the opposite trend, reaching a minimum at a spacing of 9 μm, where fused silica exhibits the weakest laser-damage resistance.