The cushioning packaged system is always predigested as a two-degree-of-freedom system. In order to study the effect of nominal frequency ratio, damping ratio, mass ratio and the amplitude of the terminal peak saw tooth pulse on the shock response spectrum of the critical element and the main part reaction of cushioning packaging system material, a method based on fourth order Runge-Kutta algorithm is proposed in this paper. The experimental results show that the proposed method has an important application in the design of cushioning packaging.