An irregular-shaped triple-mode cavity resonance structure, comprising a cavity and a cover plate, wherein the cavity is internally provided with a dielectric resonance block and a dielectric support frame, wherein the cavity is of a cube-like shape, at least one end face, correspond to the dielectric resonance block, of the cavity is concave, the dielectric resonance block is of a cube-like shape, at least one end face of the dielectric resonance block is convex, the dielectric support frame is respectively connected with the dielectric resonance block and an inner wall of the cavity, the dielectric resonance block and the dielectric support frame form a triple-mode dielectric resonance wherein the triple-mode comprises a base mode, and a dielectric constant of the dielectric support frame is smaller than a dielectric constant of the dielectric resonance block; a ratio K of a size of a single side of the inner wall of the cavity to a size of a corresponding single side of the dielectric resonance block meets: transition point 1 ≤ K ≤ transition point 2, such that a Q value of a higher-order mode, adjacent to the base mode, of the triple-mode dielectric resonance structure is transited into a Q value of the base mode of the triple-mode dielectric resonance structure, a base mode resonance frequency after transition is equal to a base mode resonance frequency prior to transition, a Q value of the base mode after transition is greater than a Q value of the base mode prior to transition, and a Q value of the higher-order mode, adjacent to the base mode, after transition is smaller than a Q value of the higher-order mode, adjacent to the base mode, prior to transition; the triple-mode dielectric resonance structure is internally provided with a coupling structure for changing an orthogonal property of a triple-mode electromagnetic field in the cavity; and the triple-mode dielectric resonance structure is internally provided with a frequency tuning device for changing a resonance frequency of the triple-mode in the cavity; wherein the ratio K is configured to meet the conditions 1.03 ≤ transition point 1 ≤ 1.3, 1.03 ≤ transition point 2 ≤ 1.3, transition point 1 < transition point 2. at least one end face, correspond to the dielectric resonance block, of the cavity is concave, the dielectric resonance block is of a cube-like shape, at least one end face of the dielectric resonance block is convex, the dielectric support frame is respectively connected with the dielectric resonance block and an inner wall of the cavity, the dielectric resonance block and the dielectric support frame form a triple-mode dielectric resonance wherein the triple-mode comprises a base mode, and a dielectric constant of the dielectric support frame is smaller than a dielectric constant of the dielectric resonance block; a ratio K of a size of a single side of the inner wall of the cavity to a size of a corresponding single side of the dielectric resonance block meets: transition point 1 ≤ K ≤ transition point 2, such that a Q value of a higher-order mode, adjacent to the base mode, of the triple-mode dielectric resonance structure is transited into a Q value of the base mode of the triple-mode dielectric resonance structure, a base mode resonance frequency after transition is equal to a base mode resonance frequency prior to transition, a Q value of the base mode after transition is greater than a Q value of the base mode prior to transition, and a Q value of the higher-order mode, adjacent to the base mode, after transition is smaller than a Q value of the higher-order mode, adjacent to the base mode, prior to transition; the triple-mode dielectric resonance structure is internally provided with a coupling structure for changing an orthogonal property of a triple-mode electromagnetic field in the cavity; and the triple-mode dielectric resonance structure is internally provided with a frequency tuning device for changing a resonance frequency of the triple-mode in the cavity; wherein the ratio K is configured to meet the conditions 1.03 ≤ transition point 1 ≤ 1.3, 1.03 ≤ transition point 2 ≤ 1.3, transition point 1 < transition point 2.