The invention relates to a sound insulation cavity structure for a capacitor. The sound insulation cavity structure comprises a sound insulation cavity case, and is characterized in that a vibration isolation and sound absorption material is arranged inside the sound insulation cavity case; the vibration isolation and sound absorption material is arranged between two large surfaces of a sound insulation cavity; the sound insulation cavity is divided into cavities. The vibration isolation and sound absorption material is fixed in the sound insulation cavity through a damping material; the damping material is arranged in the two cavities separated by the vibration isolation and sound absorption material so as to tightly clamp the vibration isolation and sound absorption material. One or a plurality of damping materials are used, and are in a round shape, a strip shape or a square shape. The damping material uses rubber, plastics, fiber, cork wood, felt or springs. The vibration isolation and sound absorption material uses a metal plate, a plywood or a micro-perforated plate. Compared with an ordinary sound insulation cavity, the sound insulation cavity structure for the capacitor has the advantages that better sound insulation performance is realized; the noise of the capacitor can be further reduced.