Digs or scratches generated during the processing and application of optical components seriously affect the surface quality of these components. The scattered light caused by digs or scratches is divided into two parts based on Peterson’s defect scattering theory: geometric refraction or reflection from the surfaces inside scratches or digs and diffraction of light that passes around the scratch or dig. The analytical formulas for the bidirectional reflection distribution function of the scratches or digs are derived considering the light-blocking effect of the digs and scratches and the boundary conditions for the disappearance of diffraction around the digs, and by combining the theory of defect scattering with the new national standard of GB/T 1185-2006. Then, angular resolved scattering and total scattering are analyzed under different defect grade numbers. The results show that the total scattering of the surface defect is approximately linearly proportional to the area of the defect. On this basis, herein, a surface quality inspection method based on total scattering measurement is proposed, and the surface defect thresholds of optical components are analyzed.