The geometric nonlinear dimensionless dynamical equations of suspension spring system were developed and the maximum shock response spectra were obtained under the action of rectangular pulse. The effects of the dimensionless peak pulse acceleration and damping ratio on the shock spectra were discussed. The results showed that the effects of dimensionless pulse peak, the angle of suspension spring and the damping ratio of the system are particularly noticeable; the damping can obviously decrease the maximum shock response acceleration of the system. The purpose was to provide reference for design of shock absorber with suspension spring system.