A lens central thickness measurement method based on low coherence interferometry technique is presented. The cavity measurement structure is designed to measure the central thickness of the material with unknown refractive index. The measurement system is an all-fiber structure including low coherence measurement and laser ranging. The design of common optical path of low coherence measurement structure reference arm and laser ranging structure reference arm reduces the influence of environmental disturbances and obtains a higher measurement stability. The interference signal can be located and extracted by seven-step phase shifting method. By using the balanced differential structure of low coherence measurement method, the direct current item in the interference signal is removed and the positioning accuracy of the weak signal is improved. The experimental results show that the measurement accuracy for Invar standard block from the cavity measurement structure is below 0.5 μm. The system can realize high precision measurement of lens central thickness, and satisfy measurement request of high precision optical system.