Abstract: To address the installation challenges of a 2-m ring Gregorian telescope system, and similar optical systems with a small width-to-radius ratio, we propose a detection method combining local interferometry with a comparison model. This method enhances the precision of system calibration by establishing a dataset that delineates the relationship between secondary mirror misalignment and wavefront aberration, subsequently inferring the misalignment from interferometric detection results during the calibration process. For the 2-m ring telescope, we develop a detection model using five local sub-apertures, enabling a root-mean-square detection accuracy of 0.0225\lambda (\lambda = 632.8\;\mathrm\;\rm nm) for full-aperture wavefront aberration. The calibration results for the 2-m Ring Solar Telescope system indicate that the root-mean-square value of sub-aperture wavefront aberration reaches 0.104\lambda , and the root-mean-square value of spliced full-aperture measurement yields reaches 0.112\lambda . This method offers a novel approach for calibrating small width-to-radius ratio telescope systems and can be applied to the calibration of other irregular-aperture optical systems.