The invention provides a damping fin for transformer core lamination and a preparation method of the damping fin. The damping fin is prepared from the following components in parts by weight: 100 parts of nitrile rubber, 1-2.5 parts of a vulcanizing agent, 5-8 parts of an active agent, 0.5-2 parts of an accelerant, 50-80 parts of a filler, 1-4 parts of an anti-aging agent, 30-50 parts of a plasticizer and 0.3-1 part of a scorch retarder. The damping fin has excellent mechanical property and is oil-resistant, high-temperature resistant and high in strength, and the damping coefficient is greater than 0.4.