Abstract: It order to solve the problem of scattering modulation of subsurface damage in optical elements, the transmission process of light beam in the subsurface damage medium is simulated using the finite element method. The effect of different factors on the light scattering characteristics of focused light beam in media with subsurface defects is studied. The information of subsurface damage can be obtained and evaluated through optical field distribution and variation curves of intensity that contain information of subsurface damage. These research results provide an important theoretical guidance for the exploration of high feasibility, practical, quantitative, nondestructive detection technology of the subsurface damage.