Computer-aided alignment (CAA) is an effective method to improve the imaging quality of high-precision,complex,and off-axis optical systems. A computer-aided alignment method for off-axis reflective zoom systems is proposed. Due to the varying optical characteristics of a zoom system,sensitivity matrices are used in the alignment rather than a single matrix. Thus,the computer-aided alignment of a zoom system can actually be considered as a series of independent alignments of with different configurations. Each alignment in this series includes the calculation of sensitivity matrix and difference in aberrations between the actual system and the designed system,and the determination of misalignments. For this purpose,a new mathematical model is established. By numerical experiments and comparison of the image qualities between the pre-aligned and post-aligned systems,the feasibility of the CAA method is demonstrated.