The axis of precise optical systems is sensitive to the mount platforms structural deformation and vibration, and the puny structural deformation and vibration are able to directly affect the optical system stability and light-beam alignment precision. This paper analyzes the vibration and noise reduction design defect of traditional rigid connection and spherical joint connecting structure of optical mount platform. By adjusting the mount platforms support and sealing connection, the design of flexible sealed connection between the amount platform and resonator was brought forward. The modal analysis of the double-layer platform frame was carried out with ANSYS finite element method, the beam spot jitter experiment was completed. The modal analysis showed that the first order modal frequencies of the two platforms were increased to 126.5 Hz and 172.3 Hz after optimization with a large folded-cavity. The design adopted the large folded-cavity was tested with a He-Ne laser, the results show that the near-field beam spots typical position and profile changed punily during the resonator box evacuation, and the far-field beam spot jitter angle approached 3.73 (RMS) during the continuous laser operation.