To explore the mechanical properties of Corrugated Steel Plate with relieving slab, using a Corrugated Steel Plate as a numerical example, the numerical analysis model was established based on equivalent stiffness method and the model is proved reasonable. Furthermore, the mechanical properties of the Corrugated Steel Plate with relieving slab under vehicle loads are analyzed, and the conclusions were drawn: relieving slab can not effectively reduce the internal force of the Corrugated Steel Plate structure under dead load, maybe make the internal force of the structure higher; relieving slab can effectively reduce the bending moment of the structure under the vehicle loads, about 50% lower than which does not set a relieving slab, but the relieving slab has little effect on the axial force of the structure under the vehicle loads; the most unfavorable conditions is the maximum axial load act on the crown, which can produce the maximum bending moment and should be considered during design phase.