After considering the characteristics of non-homogeneous items of state space equation which is conversed by structure dynamic equation,simplified precise immediate integration method is presented.Though blocking computing matrix,it can decrease the calculation amount of matrix multiplication.Meanwhile,the different simplified formats are presented when computing Duhamel integration with Trapezium formula、Simpson formula、Cotes formula and Gauss formula.Compared with the precise immediate integration method,simplified method can maintain the calculation accuracy and improve the calculation efficiency at the same time.The results of examples show the validity of simplified method in this paper and it will have large advantage in dealing with large-scale and long time simulations.