Abstract: A new proposal-dominant factor method-for analyzing the dynamic behaviour of gas turbine is suggested by utilizing the results of field identification by pseudo random binary signal and combining with the theoretical analysis. The basic concept can be stated as follows.though the dynamic behaviour of gas turbine is different for each operating point,one of the parameters of the gas turbine can be selected as the dominant factor dictating its dynamic response. This parameter is the partial derivative of air flow rate Gc versus speed of the gas generator rotor n1, that is (dGc/dn1) in the compressor chart. Therefore, it isreadily to establish the simplified mathematical model of gas turbine as a nonlinear system. At first,we calculate the linear model for the design point, and then in accordance with the variation of this dominant factor the dynamic model for the other operating points can be approximately determined (for steady and unsteady regimes). The feasibility of this method is proved by experiment.