In order to realize the alignment of a large aperture telescopic system and to improve the image quality, the alignment aberration and computer-aided alignment technique are investigated. Firstly, the perturbation error of a RC telescope due to the displacement and tilt of a secondary mirror is analyzed in an alignment process. Based on the feature that the coma-free point and the center of curvature are chosen as the rotating centers during the adjusting process，the effect of choosing two different points on the optical aberration and pointing errors is emphatically analyzed. Then, according to wavefront aberration theory combining with optical software Code V，the special sensitivity matrixes of constant coma and linear astigmatism of telescope system are studied based on the computer aided alignment principle, and the alignment technique is realized by programming and emulating. Finally, combining the project applications, 1 m telescope system is adjusted and aligned. Experimental results indicate that the RMS of system after alignment reaches 0.144 5λ,which is greatly superior to 1.214λ before alignment. The results prove that the method has good accuracy, anti-interference ability and practical application values.