Abstract: In order to improve the dynamic characteristics of the secondary mirror support structure of a large aperture space telescope and obtain better imaging quality, a method of damping vibration by coating a hard damping coating on the thin-walled beam of the secondary mirror support was proposed based on the comparison of the advantages and disadvantages of the current methods. Firstly, the optimal coating thickness and elastic modulus of the hard coating were analyzed with the objective of optimizing the comprehensive performance of the hard coating and secondary mirror support composite structure. Then, the acceleration response curve of the secondary mirror support structure before and after the hard coating was analyzed with ANSYS. Finally, the effects of the hard coating on the optical imaging performance were analyzed by using Zemax and Matlab software respectively from the rigid body displacement and the mirror surface profile change. The analysis results show that the acceleration response of the secondary mirror assembly in X, Y and Z directions decreases by 30% to 50% compared with that before coating under a sinusoidal excitation of 6 g magnitude, and the imaging quality and the precision of the secondary mirror model of the optical system are also greatly improved.