The invention discloses a rear panel assembly for a silencing box shell structure. An adhesive tape is fixedly mounted on the front side surface of a rear panel, a cable protecting ring is mounted ina mounting hole in the left side surface of the rear panel, an axial flow fan is fixedly mounted on the left side surface of the rear panel, and an exhaust sealing device is mounted on the left side surface of the rear panel through a cross recess head screw, a washer, a spring washer and a nut. An upper damping plate is fixedly mounted on the top surface of the inner side of the rear panel, and upper sound absorbing cotton is fixedly mounted on the upper damping plate. Side damping plates are mounted on the left side surface and the right side surface of the inner side of the rear panel, andside sound absorbing cotton is fixedly mounted on the side damping plates. A rear damping plate is fixedly mounted on the rear side surface of the inner side of the rear panel, and rear sound absorbing cotton is fixedly mounted on the rear damping plate. A handle is mounted on the top surface of the outer side of the rear panel through a blind rivet. The rear panel assembly is simple and compact in structure, simple in processing technology, low in cost and great in sound insulating effect.