The optical transfer function of 30m telescope tertiary mirror under arbitrary forms of vibration was obtained by numerical method, and the accuracy was analyzed. The normalized point source sensitivity was introduced to present the influence of internal vibration on the light beam transmit function. To verify the theoretical analysis, a larger aperture telescope was experimented. In the experiment, a multi-accelerometer method was used, the decoupling of the mirror rigid body motion and the constrain of the testing error were realized by data collected by the residual accelerometers. The results demonstrate that, under the influence of the internal vibration source, the normalized point source sensitivity degrades from 0.99996 to 0.99992. After passing the filter the output force is 0.075N.