The invention provides a filter and a coupling structure thereof. The filter comprises a shell, resonators and a coupling structure, wherein the shell comprises a bottom plate, side plates and a cover plate; the side plates are perpendicularly arranged on the bottom plate; the cover plate is fixed above the side plates through screws to form a sealed cavity; a partition plate is detachably mounted on the bottom plate to divide the cavity into multiple resonant cavities; the two ends of a coupling sheet are extended into the adjacent two resonant cavities; the resonators are mounted in the resonant cavities; the coupling structure comprises the partition plate and the coupling sheet; a coupling window is formed in the top of the partition plate; a bending edge which is bent towards the two sides of the partition plate is arranged at the bottom of the coupling window; the coupling sheet is detachably mounted on the bending edge; and downward turning edges are arranged at the two ends of the coupling sheet, and the coupling intensity can be adjusted based on the sizes of the turning edges. By adoption of the mode, the cover plate can be disassembled and assembled for multiple times so as to perform debug and repair conveniently; and the coupling structure is simple and reliable, so that the production efficiency and the reliability of the filter are greatly improved, the production cost is lowered, and the rejection rate of the product is reduced.