Abstract: The traditional interferometry method of large-aperture optical element relies on artificially changing the beam expanding lens and optical path structure according to different test samples. This method inevitably introduces some systematic errors. Therefore, a set of corresponding dual-line control scheme was proposed according to the functional requirements of the dual-optical path interferometer and the simulation experiment. Through the cooperation of bluetooth communication, serial communication and mechanical structure, the optical path could be converted and calibrated for many times, so that the changing position of the optical element after each switch of the measurement diameter was fixed, and the real-time status was displayed in the interactive interface based on microsoft foundation classes (MFC). The results show that under 450 mm measurement diameter, the measurement repeatability of PV₁₀ can reach 0.004 λ, and that of root-mean-square (RMS) can reach 0.000 4 λ. Under 100 mm measurement diameter, the measurement repeatability of PV₁₀ can reach 0.000 8 λ, and that of RMS can reach 0.000 16 λ. Finally, the experimental results show that the system ensures the superior measurement efficiency and repeatability, which provides reference value for the research and development of dual-optical path interferometers.