We describe characteristics of diversity and distribution of oak forests on the Daegok-cheon gorge of the Southeastern Korean Peninsula, the oldest prehistoric site, in view of a sort of food resources of acorns. The Zürich-Montpellier School’s method was adopted for field investigation on the oak dominant stands. A total of 20 phytosociological relevés composed of 193 taxa were analyzed by syntaxonomy and ecological flora. The Daegok-cheon’s oak forests occupied 36.9% (513,374 m2) of the surveyed area, and its 99% (507,677 m2) was Quercus variabilis and Q. serrata stands. Oak forests of the Daegok-cheon gorge are a kind of regional vegetation type characterizing by the high relative net contribution degree (r-NCD) of Platycarya strobilacea and Sapium japonicum, which are an edaphic type of the xerophilous and thermophilic oak forests. The region of the Daegok-cheon petroglyphs is defined as an ecoregion with rich acorn supply and abundant water resources, and the warmer environment, which attracts prehistoric man.