In the polishing process of optical components, subsurface damage such as cracks will inevitably appear, which seriously influences the performance and life of the optical components. In this paper, we simulate the process of fluorescence microscopic measurement system based on the fluorescence characteristics of quantum dots, establish the subsurface damage model of optical components by the finite difference time domain (FDTD) and get the relationship between the geometrical characteristics of subsurface damage and the electromagnetic field of quantum dots fluorescence in fused silica. The detected fluorescence intensity curve reflects the width and depth of subsurface microcracks. The experiments show that the fluorescence electromagnetic field intensity of quantum dots enhances with the increase of the subsurface cracks width and the fluorescence electromagnetic field intensity of quantum dots weakens with the increase of the crack depth. The results have theoretical guidance value for exploring the subsurface nondestructive detection methods.