This study was conducted to analyze the characteristics of plant communities within the Chilgok Gasansanseong Fortress of Palgongsan National Park and to establish fundamental data necessary for its long-term management and conservation. Chilgok Gasansanseong Fortress is a cultural heritage site located within Palgongsan National Park and is classified as a Park Nature Conservation Area under the National park zoning system, indicating its high conservation value. The analysis of 96 plots within the Chilgok Gasansanseong Fortress, identified a total of eight communities using TWINSPAN and DCA analysis: Pinus densiflora–deciduous broad-leaved community (Ⅰ), Pinus densiflora community (Ⅱ), Carpinus laxiflora– Pinus densiflora community (Ⅲ), Pinus densiflora–Carpinus laxiflora community (Ⅳ), Fraxinus rhynchophylla–Acer pictum community (Ⅴ), Fraxinus rhynchophylla–Alnus japonica community (Ⅵ), Robinia pseudoacacia–Castanea crenata community(Ⅶ), and Zelkova serrata–deciduous broad-leaved community (Ⅷ). These communities can be categorized into artificial forests dominated by planted species such as Robinia pseudoacacia, Castanea crenata, and Alnus japonica (Ⅵ, Ⅶ) and natural forests dominated by native species (Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅷ). It is believed that through management, artificial forests can be guided to undergo succession into natural forests that are aligned with the regional climatic conditions. This approach is expected to provide essential baseline data for the conservation of natural resources in national parks. Since this study focused on Chilgok Gasansanseong Fortress, it is limited in its ability to comprehensively analyze the characteristics of plant community structure across the entire Palgongsan National Park. Therefore, additional studies should be conducted on other areas within Palgongsan National Park.