Abstract: A series of equivalent simplified methods were investigated in this paper and equivalent parameters were calculated for sandwich plate with polyurethane elastomer core reinforced by crossing walls. Firstly, a global equivalent method was discussed in case of ignoring the shear deformation of the core. In this way, the reinforced structure could be made equivalence to orthotropic thin plate and stiffness coefficients equations were presented. Secondly, when considering shear deformation of the core, equivalent elastic coefficients of the core compounded by crossing walls and polyurethane elastomers were also given by theoretical derivation. Finally, the equivalent orthotropic modules for the polyurethane core with crossing walls were analyzed by finite element method (FEM) based on equivalent strain energy density. And the results show that the error between theoretical derivation and FEM is less than 10%.