For a large aperture ground-based telescope with segmented primary mirrors, in order to guarantee the continuity of the figure of the total mirrors, a new interferometric detection method was put forward to detect the phase errors between the segmented mirrors, and correct the misaligned segments correspondingly. This method could make the telescope achieve optical image with diffraction limit. The segment misalignment errors between the segments include tip/tilt error and piston error, the segment piston error between the individual segments must be reduced to less than 100 nm. We have considered an interferometric piston error measurement system based on a Michelson interferometer layout for accomplishing such object. The innovation introduced in the optical design of the interferometer is the simultaneous use of both monochromatic and white-light source that allowing the system to measure the piston error with an uncertainty of 8～10 nm in the range of 45～60 μm. Simultaneously a detailed description about the optical system layout and the theoretic interferograms was gotten.