This study was conducted to provide fundamental ecological information necessary for establishing ecological management strategies to restore naturalness and enhance biodiversity in Larix kaempferi plantations located within Gayasan National Park. A total of 129 forest stands were surveyed, and vegetation types were classified using Two-Way Indicator Species Analysis (TWINSPAN). While species composition patterns were further analyzed with Detrended Correspondence Analysis (DCA) to examine their relationships with environmental gradients. In addition, the ecological characteristics of each vegetation type (including total percent cover (per 100 m²), importance value, species diversity index, and composition of indicator species) were compared and analyzed. The analysis identified six distinct vegetation types: Styrax japonicus–Lindera glauca type, Smilax sieboldii-S. nipponica type, Hydrangea serrata-Persicaria filiformis type, Fraxinus sieboldiana-Rhododendron mucronulatum type, Quercus aliena-Carex fusanensis type, and Acer pseudosieboldianum type. The differentiation of these vegetation types was interpreted as the result of complex interactions among ecological and historical factors, including elevation, hydrological conditions, disturbance history, and plantation age. Mean relative Importance Value (MIV) analysis showed that Larix kaempferi had the highest dominance at 40.4%, followed by various deciduous broadleaf tree species such as Q. serrata and Q. mongolica, suggesting potential successional trajectory. These findings provide baseline data for understanding the vegetation structure and biodiversity characteristics of L. kaempferi plantations in Gayasan National Park and are expected to contribute to the scientific foundation for ecological conservation and sustainable forest management in the future.