Abstract: A highly efficient domain decomposition method based on finite element tearing and interconnecting algorithm is presented for analysis of finite periodic electromagnetic structures.The original domain is partitioned into several nonoverlapping subdomains to decrease computational scale and complexity.The general variational principle is employed in communicating information between subdomains with Lagrange multipliers,which yields a reduced-order coarse problem.To improve scalability of the algorithm,basic subdomains are introduced.The results show that the method is highly efficient and scalable even on a sequential computational platform.Compared with traditional methods,the proposed method is more efficient,especially for the problems with geometric repetitions,such as photonic crystals.