For the large aperture telescope with segmented primary mirrors, a low-coherence-source interferometric detection system based on the Michelson interferometric principle was put forward to detect the phase error between the segmented mirrors, correct the misaligned segments and achieve the mirror coplanar. The concrete structure of the interferometric detection system with the low-coherence source was presented, and the detection principle of the interferometric detection system was narrated. Double-center-wavelength combination low-coherence-source light sources were applied to detecting the phase error of the segmented mirrors and the minimum signal-to-noise ratio was analyzed. The result shows that the application of the double-central-wavelength combination low-coherence source light sources system largely raises the ability of signal distinguishing of the center fringe of the interferograms, improves the measurement accuracy, and makes the low-coherence-source interferometric detection system extract the phase error with high precision.