This paper presents a research on the modal analysis and the time serics model. for the general synthetic damped system which takes into account both viscous damping and structural damping. The representation for the transfer function matrix is derived by means of the properties of this system in the state space Through the relationship of Laplace transform and Z-transform, the ARMA time series model for this system is obtained. Therefore, a theoretical basis for identifying the modal parameters of this system is providcd by the methods of frequency. domain and time series.