For the high-order process objects with time delay in industrial production, it is difficult to implement the direct design of the controller and the traditional model order reduction method due to the complex structure of the controller. In addition, the interference of noise to the controller generate unsatisfactory results. In order to solve this problem, this paper proposed a frequency domain identification method of high order plus time delay model, through the process plant in the control circuit of input and output signal frequency spectrum analysis and Laplace transformation, it was concluded that the frequency of the process plant on important frequency could response characteristics, and the least square method is used in both amplitude and phase fitting a first or second order plus pure lag transfer function, finally the plant model is obtained. At last, MATLAB simulation results verified the effectiveness and accuracy of the proposed method.