Abstract: An adaptive reference system time domain identification method which can trace the time variation characteristics of multidegree nonlinear vibrating structures with complex dampings is presented in this paper. This approach transforms or maps the nonlinear structural system into a linear one based on a known reference system(linear),and establishes ARMA model and Yule-Walker equation.It makes it possible to identify the nonlinear structures by means of using the existed linear identification methods.An example of a hydro-tsucture located at high seismic in tensily region (8 degree)is presented to illustrate the effectiveness and creditability of this new technique.