Subsurface damage (SSD) produced in traditional optical fabrication will reduce service performance and lifetime of optical elements. It is necessary to detect and control the subsurface damage in the fabrication process. Destructive and nondestructive detection methods of subsurface damage are analyzed. The merits and demerits of these detection methods are also discussed. The gap of subsurface damage detection technologies at home and abroad is presented, and the trend of subsurface damage detection technology is described.