Abstract: Several bore-sight methods for multi-spectral optical axes used nowadays were compared. Based on a large aperture collimator, a new bore-sight method for optical axes parallelism was put forward by using CCD technology. In this method, the ZYGO interferometer was used for accurately focusing. By comparing the center coordinates of the conjugated image on CCD of the target with the center coordinates of the laser spot of the system under test, the parallelism between the visible axis or infrared axis and the laser axis was calculated. The focal plane of large aperture off-axis paraboloid was determined and analyzed, and the center position of the laser spot was determined as well. The measurement uncertainty was analyzed and the uncertainty of 5 was obtained.