Woody plant seedlings are an essential part of the forest ecosystem, and their ecological processes of settlement, survival and growth are potential indicators and screening for forest vegetation regeneration. To explore the regeneration and succession mechanism of the community of the subtropical evergreen broad-leaved secondary forest in Hangzhou Wuchao Mountain, Zhejiang Province, the species composition, quantitative characteristics and stem base diameter (SBD) classes of the natural regeneration seedlings in a 150 m² plot were counted based on the sample plot method. On this basis, the nearest neighbor analysis (NNA) and the point pattern method of Ripley's K function were adopted to analyze the regeneration dynamics of the main dominant tree species and their spatio-temporal distribution patterns. Results showed that (1) tree seedlings in the plot are rich in species composition. A total of 811 seedlings were investigated, belonging to 12 families, 20 genera and 27 species, among which Lauraceae, Fagaceae, Theaceae and Symplocaceae are the main dominant families. (2) Machilus thunbergii, M. leptophylla, Camellia fraterna and M. spauhoi were identified as dominant understory plants, ranking the top four position in importance values of all investigated species. Meanwhile, the violin plot of the SBD classes further shows that the populations of these species belong to the fast-growing type, stable-growing type, slow-growing type and stable type, respectively. (3) M. thunbergii, M. leptophylla and M. spauhoi are mostly clustered at the small SBD classes and small scales. With the increase of growth and spatial scale, the clustering intensity firstly increases and then decreases, and finally changes to a discrete distribution or a random distribution. As the growth and development and the spatial scale increase, the aggregation intensity fluctuates and eventually transforms to a discrete distribution, which can be regarded as a mid-term succession tree species. Meanwhile, the three trees are different in the intensity of aggregation, sorted as M. thunbergii > M. leptophylla > M. spauhoi. The population density of Camellia fraterna is relatively low, and it is randomly distributed on small SBD classes and small scale. With the increase of growth and spatial scale, the aggregation intensity fluctuates, and finally becomes a discrete distribution. Therefore, C. fraterna can be regarded as the middle stage of succession. This study initially revealed the population structure and distribution pattern in the succession process of Wuchao Mountain woody seedling population on a small scale, which can provide a theoretical basis for subtropical forest management and vegetation restoration.