The optical surface error is one of the key factors to guarantee the image quality for space telescopes. Increasing aperture and minimizing structural mass result in a relatively lightweight and flexible telescope mirror, whose surface figure is vulnerable to micro-vibration disturbances. Unfortunately, there are a variety of disturbances in space, such as stepper motors, momentum wheels, and cryocoolers. In order to investigate the effect of dynamic optical surface errors on disturbances, a method based on modal superposition and Zernike polynomials(ZPs) fitting was proposed. On the basis of normal mode, the response of an opto-mechanical structure under force excitations could be approximated by the sum of normal modes of the system. For each mode shape, the optical surface could be fitted as a linear combination of ZPs, which were typically used to describe optical surface errors and represent the aberrations of optical systems. Then, modal superposition technique was applied to compute the combined response of surface error. Finally, the dynamic response of optical surface error to disturbances was given in terms of ZPs. So, the influence of disturbances on the aberrations of optical system can be predicted straightforwardly.