Abstract: In order to study the effect of cavity thickness on the seismic properties of foam core sandwiched wall, model tests and numerical simulations of the in-plane and out-of-plane seismic properties of 20 patches of foam core sandwiched wall and 2 patches of solid wall are carried out, and the validity and the accuracy of the numerical simulations are verified. The numerical simulations of the in-plane and out-plane seismic properties of the foam core sandwiched wall of different cavity thicknesses are carried out. The relative displacement difference is most remarkably affected by the cavity thickness when the foam core sandwiched walls are loaded in-plane; the seismic bearing capacity is most remarkably affected by the cavity thickness when the foam core sandwiched walls are loaded out-plane. In general, the cavity thickness has a greater effect on the in-plane seismic property than on the out-of-plane seismic property. The deformation coordination capacity will be reduced remarkably when the cavity thickness increases. It is therefore recommended that cavity thickness is not greater than 100mm in the buildings of high earthquake intensity regions.