The warm temperate deciduous broad-leaved secondary forest in Dongling Mountain is relatively well-preserved. Species compositions and community structures are important in the process of secondary forest succession and are also the basis for the next succession. To further study the secondary forest dynamics of biodiversity succession and conservation mechanisms, a relatively large 20 hm² experimental forest fixed monitoring sample plot in Dongling Mountain was chosen, and the species composition, diameter class structures, and spatial patterns of live standing trees and snags of the warm temperate deciduous broad-leaved secondary forest were analyzed. The results showed that (1) there were 103702 live standing trees with DBH ≥ 1 cm, and a density of 5185.1/hm² in the plot; there were 4543 snags with a density of 204.9/hm², both of which included the quantities of branches and sprouted branches. There were 58 species of live standing trees with DBH ≥ 1 cm in the plot, belonging to 33 genera and 18 families; and 33 species of snags with DBH ≥ 1 cm belonging to 23 genera and 15 families; (2) in terms of overall distribution, the diameters of live standing trees and snags fluctuated, showing a trend of first increasing and then decreasing, and the individual abundance of smaller sized trees had significant advantages in distribution; (3) for live standing trees, as the diameter increased, the aggregation intensity decreased, with 10 cm ≤ DBH < 20 cm and DBH ≥ 40 cm, whereas regular, random and aggregate distributions occurred with 20 cm ≤ DBH <40 cm in a scale of 0-50 m. For snags, when DBH < 5 cm and the scale was close to 30 m, a random distribution appeared; moreover, when DBH ≥ 40 cm and the scale was close to 30 m, there was a continuous random distribution, and a clumped distribution occurred when 5 cm ≤ DBH < 40 cm. The spatial distribution patterns showed that sizes of diameters were complementary in spatial structures, and individuals with different diameters occupied different niches in the sample plot; (4) the correlation analysis between different sizes of live standing trees and snags showed that the smaller the diameters and scales, the more obvious relevance, whereas the spatial correlation of large sizes and scales were gradually weakened. Snag production was affected by the density dependence, status and stages of succession of live trees, and habitat heterogeneity; however, the mechanisms involved still need to be studied further.