Abstract: A shock response spectrum method for multi-body systems was presented. Take a rigid-flexible-multi-body system under base shock excitations for example, the theoretical foundations of that method were described, including: firstly, to obtain the system state vectors and natural modes by transfer matrix method; secondly, to build differential equations of system bodies in a coordinate relative to base, and then to decouple equations by the orthogonal of augmented eigenvectors, the maximum responses in each modes were thus obtained by the definition of shock spectrum; lastly, the time –varying responses were obtained by mode combination. The utility and validity of the proposed method were confirmed by an application example at last.