The invention discloses a deformable cavity device which is used for solving a technical problem that the noise reduction effect of the existing deformable cavity device is poor. The technical scheme is that the deformable cavity device comprises a front wall surface, a first pin shaft, a bottom plate, a second pin shaft, a rear wall surface, a third pin shaft, a rear edge and a guide rail and further comprises a front edge and a fourth pin shaft. The front edge is fixed; the front wall surface is hinged with the front edge through the fourth pin shaft; the bottom plate is hinged with the front wall surface through the first pin shaft; the rear wall surface is hinged with the bottom plate through the second pin shaft; the rear edge is hinged with the rear wall surface through the third pin shaft; and a slide block on the rear edge is mounted in the guide rail and can horizontally slide. Through simultaneously driving the rear edge, which can horizontally slide along the guide rail, and the front wall surface, which can rotate around the fourth pin shaft, the inclination angles of the rear wall surface and the bottom surface of a cavity can be changed and the inclination angle of the front wall surface of the cavity can be also changed so that the cavity device is deformed. Compared with the prior art, the deformable cavity device has a better noise reduction effect.