In order to expand the detection range of the piston error in the fine common phase stage, reduce the detection process and reduce the installation and calibration requirements in the multi-method detection connection process, this paper proposes a segmented mirror common phase detection method based on multi-wavelength interference technology. In the coarse common phase, monochromatic laser interferometry and white light interferometry are used to achieve the calibration requirements of 100 micron-level and micron-level piston errors respectively; in the fine common phase, dual-wavelength laser interferometry is used to achieve high-precision detection of micron-level piston error. Taking the two hexagonal spherical sub-mirrors cut out of the whole mirror as the test object, the red and green laser dual-wavelength phase shifting interferometer and the white light micro-interferometer are used to experimentally verify the proposed technical scheme, and the proposed technique is based on the segmented mirror shape. A relative piston error calculation algorithm based on the segmented mirror shape detection data is proposed, and a set of segmented mirror co-phasing assembly and calibration system is designed and constructed. After the calibrated piston error of the coarse common phase is on the order of micrometers, the piston error between the sub-mirrors in the fine common phase can be compensated from 601.6 nm to 16.0 nm.