Surface defect detection is the key to assessing the quality of optical surfaces. Traditional geometric optics cannot adequately explain the distribution of defects on surfaces. Herein, a method is proposed to comprehensively investigate the scattering characteristics of surface defects in precision optical components. First, electromagnetic theoretical models of surface defects with cross-sections of triangles, ellipses, and rectangles were established using the finite element method. Through simulation, the precise distribution of scattered light at the micro-nano-scale defects in the transmissive-reflective direction was obtained. Subsequently, a sophisticated dark-field microscopic testing system was designed and constructed to capture high-resolution scattered light images of standard defect samples. To effectively measure the depth of surface defects, a highly sensitive photomultiplier tube was used to measure the scattered light intensity. The measured intensity was subsequently compared with the theoretical simulation results to obtain a reference value for the defect depth. The reference values for the depth of surface defects obtained from the simulation are largely consistent with experimental results. It provides a theoretical foundation and reference for the multidimensional measurement of surface defects in optical components.