The invention discloses a broadband filter with a single-cavity four-mode cavity resonator. The broadband filter with the single-cavity four-mode cavity resonator comprises a cavity, a first port, a second port, a first perturbation metal body and a second perturbation metal body, wherein both the first perturbation metal body and the second perturbation metal body are arranged on the bottom of the interior of the cavity, both the center of the first perturbation metal body and the center of the second perturbation metal body are deviated from the center of the cavity, the first perturbation metal body and the second perturbation metal body are symmetrical with the longitudinal center line of the cavity as the center, both the first port and the second port are formed in the cavity and penetrate through the outer wall and the inner wall of the cavity, a first conductor assembly is arranged at the position of the first port, a second conductor assembly is arranged at the position of the second port, the axis of the first conductor assembly is perpendicular to the axis of the second conductor assembly, and both the axis of the first conductor assembly and the axis of the second conductor assembly are perpendicular to the longitudinal line of the cavity. The broadband filter with the single-cavity four-mode cavity resonator has the advantages that the selectivity is high, the Q value is high, both designing and machining are convenient, the fractional bandwidth is wide, and the requirements of small communication can be welled met.