Abstract: In view of the appearance of aligning error for duallayer frequency selective surface (FSS) in the practical application of curved surface, based on the coupled integral equations, the theoretical model of duallayer FSS with screens aligning error is proposed and the electromagnetic characteristics are analyzed. Combining with the periodic boundary condition, the calculating regions of each layer are reduced to one unite cell by spectral method of moment (MoM). The continuity of the induced current on the periodic boundary of conductor is considered for the FSS cell aligning error. The current distribution is predicted by RaoWiltonGlisson (RWG) basis functions which are applicable for arbitrarily shape elements. Taking squareloop FSS as an example, the accuracy of proposed method is verified and the effect of the boundary current continuity on the FSS electromagnetic characteristics is researched. The effects of the distance between two layers, the incident polarization direction and the misalignment error on the scattering characteristics of duallayer FSS are investigated.