The distance measurement of optical mirror surfaces based on low coherence interferometry is described. The system realizes lens surface distance measurement with high precision, by first using double micro-electromechanical systems (MEMS) switches to multiply enlarge the measuring range, secondly by using co-light-path laser ranging structure to realize the displacement measurement of the scanning mirror, and thirdly by using the envelope extraction algorithm to obtain the zero light path difference location of low coherence light interference signal. The whole measurement system has an all-fiber structure. Lens surface distances of Invar gauge, optical system with large air gap and optical lens group are measured with this system. Under the condition of the scanning range of 300 mm, distance measurement within the range of 0.02~550 mm by using MEMS switches is realized, and the experimental results indicate that the system possesses high measurement accuracy below 0.5 μm.Such a measurement system has important applications in optical testing and optical alignment of high precision optical systems, such as lithography exposure system, aerial camera, and laser resonator.