To measure the dynamic performance of the thirty meter telescope tertary mirror, the model based on the accerleration signal was established for parameters calculation and identification. First and foremost, under the TMT requirement, the procedure to obtian the dynamic property of the system by acceleration signal was presented. Then, by the output to the unknown excitation, the free response can be reached. After that, the polynomials fitting was used to process the transfer function obtained from the previous step to identify the model parameters. This method was then applied to a four-meter scale system, the first two orders of strcture were correspondingly 88 Hz and 107 Hz. What is more, the mode shape is also calculated and the parameters in the modle are modified by it. The work of this artile is expected to be helpful for the accomplishent of the thirty meter telescope.