The invention relates to a passive containment air cooling system. The system includes a cooling verandah on the outer surface of a containment; air in the cooling verandah flows from bottom to top. Alower guiding verandah is arranged on the outer side of the cooling verandah; an air inlet is formed in the upper end of the lower guiding verandah, and the lower end of the lower guiding verandah iscommunicated with the inlet of the cooling verandah. The system has the advantages that after an accident takes place, heat in the containment can be taken away by natural circular air cooling only,and the integrity of the containment is ensured.