The vector aberration theory shows that an optical system that has corrected the primary aberration will still have aberration performance in the state of small misalignment,which is particularly significant for airborne and spaceborne optical systems working in harsh environments.Wavefront coding technology has been proved to have a certain passivation effect on the first-order and third-order aberrations.Based on the principle of wavefront coding,this paper studies the passivation effect of the third-order phase plate on the astigmatism caused by the misalignment of the optical system from the perspective of vector aberration,and takes the Cassegrain system as an example for simulation verification.The research shows that the wavefront coding computational imaging system is not sensitive to the misalignment astigmatism caused by the tilt of components.It can maintain good imaging effect when the system is slightly misaligned.This has certain significance for reducing the difficulty of optical system installation and adjustment and enhancing the environmental adaptability of airborne and spaceborne optical systems.