Abstract: In this paper,the double-layer diagonal squarc pyramid space grids (Square on Diagonal)are idealized as sardwich plates ard analysed by the non-classical theory of Plate.In the calculating model of the analogous sandwich Plate the transverse shear deformation is taken into consideration as well as the eaupling behavior of bending deformation and Plane deformation The dasic partial differential epuation in tenth order for analogous Plate of such space grid, and the formulas for calculating internal forces of members are giren. The analytic solution expressed in double trigonometric series is presented, and design tables for calculating internal forces and displacements are worked out for space grid simply supported at its perimeter. It is also pointed out that the so-called fictitious moment method is a degenerated special case of the proposed method.