The invention provides a tunable accelerating cavity and a tuning tool thereof. The external surfaces of sidewalls of the tunable accelerating cavity are respectively provided with a first non-penetrating threaded hole and a second non-penetrating threaded hole, a first annular groove surrounding the first non-penetrating threaded hole, and a second annular groove surrounding the second non-penetrating threaded hole. The tuning tool comprises a support, tuning screws, tuning nuts and tuning threaded holes. The tunable accelerating cavity and the tuning tool are used in a matched manner, positive and negative adjustment of the frequency of the accelerating cavity can be performed, the accelerating cavities whose dimensions are inadequate and excessive can be tuned, the tuning efficiency ishigh, the tuning amount is fine and controllable, the material waste is reduced, and the designed tuning tool is advantaged by simple structure and easy operation and control.