The invention discloses a paint slag processed automobile damping plate and a preparation method thereof. The damping plate comprises the following raw materials in parts by weight: 10-120 parts of thermoplastic acrylic resin, 10-30 parts of hydrogenated castor oil, 10-20 parts of polyvinyl acetate, 45-100 parts of paint slag and 20-100 parts of industrial red mud. The invention has the benefits that as the environment-friendly polymer resin is used as a polymer material, and the cured thermosetting paint slag and the modified industrial red mud are used as filling materials for the damping plate, not only are the paint slag, the industrial red mud and other waste residues comprehensively utilized, but also the cost of the environment-friendly damping plate is lowered. Compared with the prior art, the preparation technology is simple, and the product is environment-friendly and outstanding in properties.