Abstract:When electromagnetic waves propagate in periodic media, they cannot propagate in a certain frequency range due to the bandgap of electromagnetic waves formed by Bragg scattering. In order to solve the above problem, two different types of square lattice are constructed with alumina material under the background of air, and the energy bands of three different photonic crystals are solved by the finite element method. Two of them are derived from the first sliding operation; Then, by splicing two different types of lattices, the supercell is constructed, and the topological edge state is finally realized. By analyzing the single lattice cell energy band, the position reason for topological edge state formation is summarized, and the topological edge state formed by the proposed method can regulate the passing frequency of electromagnetic wave accordingly, which provides a novel design idea for tunable microwave devices.