Abstract: Subsurface damage has been the main cause to lower the laser induced damage threshold of optics components in high power solid laser system, and one important of them is scratch. finite difference time domain (FDTD) method was used to simulate the electromagnetic distribution around column form or triangular scratch in fused silica. 2D electric field amplitude distributing is illustrated, and maximal values vs.sizes are calculated. The conclusion displays that the electric intensity is maximal when size is 2λ, which is easy to cause self-focusing, the effect can be neglected when scratch is subwavelength class or large enough. The depth is larger, the maximal value is larger when size is the same, but it becomes smaller when scratch is too deep．