Abstract: The spatial network method is used to calculate the electromagnetic wave scattering characteristic of carbon fiber composite grid structures filled with absorbing foams. Along with the periodic characteristic of grid structures，using Floquet theory to analyze the periodic boundary condition，simplifying the analytical model to a cell，then the absorbing ability of different cell sizes was analyzed from the results. The numerical analysis result shows that the absorbing ability of the carbon fiber composite grid structure filled with foams is better than that of the structures without foams. The thickness and volume fraction of the filled foams are the major factors affecting the reflectivity of the grid structure.