The invention discloses a ventilation type acoustic metamaterial sound insulation barrel for noise reduction of a transformer fan. According to the ventilation type acoustic metamaterial sound insulation barrel, an acoustic metamaterial sound insulation barrel body (1) is fixed to a sound insulation barrel support and is arranged on the outer side of the transformer fan; a plurality of layers of air channels (6) are coaxially formed in the acoustic metamaterial sound insulation barrel body (1) and are arranged at equal intervals along the central axis of the acoustic metamaterial sound insulation barrel body (1); a plurality of cylindrical barriers (7) are arranged on the surface, close to the air inlet side, in each layer of air channel (6) and protrude towards the interior of the corresponding air channel (6) so as to form a cylindrical barrier array; a cylindrical air cavity (5) communicating with the air channels (6) is formed between every two layers of air channels (6); and air is circulated in the air channels (6) communicating with the cylindrical air cavities. The ventilation type acoustic metamaterial sound insulation barrel has the advantages that when a sound wave is transmitted to the acoustic metamaterial sound insulation barrel body, the sound wave is transmitted in a zigzag mode in the air channels and runs into the wall for multiple times, so that the sound energy is consumed, and refraction can occur for multiple times, so that the sound wave amplitude can be attenuated.