A computer-aided alignment method in combining with the interferometry was proposed to optimize the detection and alignment of an off-axis three-mirror system.By using a multi-fields ZYGO interferometer, a series of Zernike coefficients were obtained to express the incorrect parameters of the system, which were then transformed into geometric aberrations as the corrected objects based on the dependence of Zernike-coefficents on Seidel aberrations.Furthermore,an optical design software was used to derive the sensitivity matrix related to the incorrect parameters and to determine the incorrect parameter mostly sensitive to the redual aberration. Consequently, the adjusted result was brought into the software to verify the selection of incorrect parameters.Experimental results show that the RMS value of the system is lower than 0.04λ after iterations, which proves the effectiveness of the method in alignment guidance.