The geometric nonlinear dimensionless dynamical equations of suspension spring cushioning packaging system were established and a new concept of damage boundary curves of the system was developed under the action of rectangular pulse. Considering the angle of the suspension spring ,a three-dimension damage boundary curve is obtained.The mathematic results of the equation are calculated by using the four steps Runge-Kutta method. Studies have shown that the dimensionless pulse peak, the angle of suspension spring and the damping ratio of the system can affect the safe region, and that increasing damping can enlarge the safe region of the system. The shock of the packed product can reduce by adjusting the parameters of the system properly. These results have important application value in design of the suspension cushioning system.