The present disclosure relates to a coupling structure of a filter. One example coupling structure of the filter includes at least two resonant cavities. Each resonant cavity includes an internal space surrounded by a resonant cavity wall, a resonant cavity bottom plate, and a resonant cavity lid. The at least two resonant cavities are sequentially connected. Each resonant cavity of the at least two resonant cavities includes one resonator. A coupling rib assembly is between every two resonant cavities of the at least two resonant cavities. The coupling rib assembly includes a first coupling rib and a second coupling rib, where the first coupling rib is connected to the resonant cavity wall and the resonant cavity bottom plate to block two adjacent resonant cavities from each other, and the second coupling rib is connected to the resonant cavity bottom plate and intersects with the first coupling rib.