A dielectric waveguide filter includes first resonant cavities, which are connected to form upper resonant cavities, and second resonant cavities, which are connected to form lower resonant cavities, wherein the upper and lower resonant cavities are correspondingly overlapped; each of the first resonant cavities has a first window coupling structure, wherein the first window coupling structure includes a first window opened at a position where the magnetic field distribution of a high-order mode in each of the first resonant cavities is the weakest, and/or a second window opened at a position where the electric field distribution of the high-order mode in each of the first resonant cavities is the strongest; and each of the second resonant cavities has a second window coupling structure corresponding to the first window coupling structure, and the first and second window coupling structures cooperate to eliminate the high-order modes of the dielectric waveguide filter.