Tiled grating is an important approach to solve the problem of grating aperture limit, however, which will meet the problem of structral stability of tiled grating. According to the requirement of operation, the tiled grating mount was used, but the stability of tiled grating mount cannot satisfy the requirement fully. In order to determine the main factors which affect the stability of the grating mount, a muti-channel vibration test equipment is used to measure the ambient vibration around grating. The test indicates that vibration of heating, ventilation and air conditioning (HVAC) are the main factors that affect the stability of grating mount. The power spectral density of test (PSD) is used to optimize the dynamic response of the grating mount and the results indicate that increase of structure damp ratio can decrease the dynamic response of grating mount. According to the finite element analysis, the joint damp of grating amount′s combination planes is increased by applying high damp material. The experiment indicates that increase of structure damp ratio not only reduces the dynamic response greatly but also prolongs the stability time.