Abstract: Community structure, species composition, and spatial organization provide critical evidence for interpreting forest ecosystem dynamics and successional trajectories. In this study, a 6 hm² forest dynamics monitoring plot in Haiyang Mountain Nature Reserve, Guangxi, was used to conduct a comprehensive survey of all woody plants with diameter at breast height (DBH)≥1 cm and to systematically analyze species composition, community structure, floristic characteristics, and spatial distribution patterns. A total of 29 911 woody stems were recorded, representing 53 families and 113 genera, with 143 evergreen species and 38 deciduous species. Seventy-one rare species (density≤1 individual/hm²) were identified. Cunninghamia lanceolata (Lamb.) Hook. and Itea chinensis Hook. & Arn. were the dominant species, with importance values (IVs) of 14.23% and 5.85%, respectively, whereas Cupressaceae and Lauraceae were the dominant families, with IVs of 13.56% and 12.67%, respectively. Floristic composition was dominated by pantropical elements at both the family and genus levels, including 12 families (22.64%) and 25 genera (22.12%). Diameter-class distribution at the stand level exhibited an inverse J-shaped pattern, whereas dominant species showed either inverse J-shaped or weakly bell-shaped (near-normal) distributions. Most dominant species demonstrated spatial aggregation at small scales. In contrast, Cunninghamia lanceolata (Lamb.) Hook. exhibited a small-scale regular (uniform) distribution and shifted toward random distribution with increasing spatial scale. These results indicate that the evergreen broad-leaved forest in Haiyang Mountain is at an early to middle successional stage, retains clear secondary characteristics, and maintains high species diversity and satisfactory regeneration. This study provides important evidence for understanding successional mechanisms in mid-subtropical forests and for guiding regional natural forest restoration.