The subsurface damage of optical components is the scratches and cracks which are produced in workpiece process. The subsurface damage will change the light field under the laser irradiation. As the laser irradiation time increases, the cracks become larger and generate scattering, which finally effect the encircled energy of laser beam. This paper proposes a new method to estimate damage depth based on the principle of subsurface damage measured by total internal reflection method. Incident and exit light waves are superimposed to form the standing wave under the surface of sample, and the polarization state and the incident angle of incident light affect the distribution of light intensity in the sample. By analyzing the relation between light intensity and incident angle of subsurface damage point, the depth of subsurface damage can be estimated through the change quantity of the incident angle.