A new lateral force resisting system (LFRS), referred to as the multi-storey cable-stayed steel moment resistant frame (CSMRF) system, was proposed in this paper. The CSMRF integrates the respective advantages of both the steel moment resistant frame (MRF) and inclined cables, thus effectively promoting the lateral resistant capacity of the original MRF. Likewise, the CSMRF renders both the dual seismic defense line and selfcentering capacity. The composition and working mechanism of the CSMRF were introduced. The floor displacement (relative to the ground) approximation formula was developed for the CSMRF under the lateral loading. The numerical analysis was made of the CSMRF with resorting to the developed approximation formula. The results show that the interstory drift and the floor displacement were significantly reduced with respect to the original steel MRF. The approximate calculation formula of elastic floor displacements for multi-storey CSMRF system can provide a theoretical basis for the preliminary design of its components.