Abstract <p>The problem of plane electromagnetic wave diffraction by thin perfectly conducting screens with perturbed geometry is considered. The numerical solution based on the method of moments is developed. The surface current is approximated with Rao–Wilton–Glisson (RWG) basis functions. The numerical solution is obtained with a fast domain-cutting algorithm. This allows to significantly reduce computational costs for multiple screen configuration changes by using a pre-calculated moment matrix. The parallel algorithm using computing on graphics processing units (GPUs) with CUDA technology is implemented. The numerical results illustrating the influence of the shape, size and position of cutouts in the screen on the distribution of surface currents are presented. A comparative analysis of the running time of sequential and parallel algorithms is presented. It is shown that the proposed algorithm provides a significant acceleration and can be effectively used for large series of computational experiments and analysis of surface current behavior on complex shape screens.</p>