The sub-surface damage of the optical elements due to grinding and polishing may destroy the uniformity of the base material, result in the scattering of incident light, and seriously affect the optical properties of the product.It is very difficult to study the scattered signal due to the complex characteristics of the damage.The laser confocal microscopy testing based on the light scattering method is a fast and accurate sub-surface nondestructive testing method.It uses the sub-surface damage to the incident light scattering modulation signal to analyze the sub-surface damage information of the optical component.Aiming at the scattering characteristics of the damage, the Finite Difference Time Domain (FDTD) method is used to establish the electromagnetic simulation model for the special damage of particles and microcracks.The scattering field distribution of the incident light is studied, and the curve of the light intensity is detected at different depths.The damage light intensity detection curve can reflect the information of the size and depth of the particles and the width and depth of the microcracks.The results of the study have important theoretical significance for the study on nondestructive detection of sub-surface damage of optical elements.