With the development of telescope technology, the aperture and field of view of telescope are becoming larger and larger, the structure of optical system is becoming more and more complex, and the difficulty of fabrication and assembly is also increasing. The speckle pattern of the focal plane of the optical system can be measured by interferometer and other testing equipment, and the Zernike coefficients can be calculated by the speckle pattern. For Cassegrain telescope, in order to obtain good imaging quality, it is necessary to correct the position of its secondary mirror. By using computer-aided alignment technology, the optical system can be real-time detected and compared with the theoretical results. By establishing a mathematical model between Zernike coefficient and misalignment, the misalignment of the components can be corrected accurately. The most widely used computer-aided alignment method is the sensitivity matrix method. Sensitivity matrix method is a method of correcting aberration by establishing mathematical model of misalignment and Zernike coefficient on the basis of analyzing aberration characteristics. The traditional sensitivity matrix method only carries out single correction. According to the meaning of Zernike coefficient, z₃、z₄、z₅、z₆、z₇ and z₈ are chosen to construct the sensitivity matrix. Based on the analysis of the shortcomings of the traditional sensitivity matrix method of the two order model, a fine tuning step was added based on the characteristics of the sensitivity matrix. The calculation method of sensitivity is improved. According to the relationship between misalignment and Zernike coefficient, the selection principle of Zernike coefficient for constructing sensitivity matrix is proposed. The traditional sensitivity matrix method is improved. For the Cassegrain system, the relationship between the Zernike coefficients and the misadjustment was analyzed, and the calibration simulation of Cassegrain system with 300 mm aperture and 0.6° field of view was carried out. The simulation results show that after correction by traditional sensitivity matrix method, the mean values of offset along x, y, z axes and tilt around x,y axes are -0.0684 mm, -0.0892 mm, 0.0015 mm, 0.0498° and -0.0444°, respectively, and the full field wavefront aberration RMS is less than 0.1λ (λ=632.8 nm). After correction by two step sensitivity matrix correction method, the mean values are -0.0018 mm, -0.0012 mm, 0.0002 mm, 0.0008° and -0.0012°, respectively, and the full field wavefront aberration RMS is less than 0.03λ. The corrected optical system reaches the diffraction limit and approaches the design position, which is obviously superior to the traditional sensitivity matrix method.