Abstract: The curvature radius of optical sphere is an important parameter to determine the properties of an optical sphere. The measurement result of the spherical curvature radius can be used to assess the quality of an optical component. Based on the theory of white light interference, a Moire raster displacement measurement system and a CCD digital image acquisition system are integrated into Michelson interferometer to form a semi-automatic measurement system for measuring the curvature radii of optical spheres. The system is accurate in measuring big curvature radii. As for the spherical radius of 71.2037mm, the standard error of 472.3μm can be obtained. The experiment result shows that the system can realize high precision measurement for big curvature radii of optical spheres.