China has the largest and widest karst regions in the world, which is mainly distributed in the subtropical mountainous regions of southwest China where a unique type of karst vegetation grows. However, the karst forests in these regions have been degraded seriously due to strongly anthropogenic disturbance over many years. Therefore, vegetation thicketization and even rocky desertification have occurred in most karst regions in southwest China. The fragmented karst secondary forest in Puding County is a typical representative of the north subtropical forest vegetation in central Guizhou Province, and can be used as a sample for monitoring the vegetation structure and dynamics in this region. In this study, a 2 hm² (200m×100m) permanent forest plot was established in Tianlongshan in Puding County. Within this plot, all woody plants with a diameter at breast height (DBH)≥1 cm were mapped and identified at species level. Based on these data, the community composition and spatial structure of the vegetation community were analyzed. Results indicated that there were 14, 025 woody plant individuals belonging to 66 species, 55 genera and 34 families. The families with high importance values (Ⅳ) are Fagaceae, Juglandaceae, Lauraceae, Saxifragaceae, Rosaceae, Betulaceae, Rhamnaceae, etc. There were more temperate elements (52.7%) than tropical elements (40.0%) found both at genus level, which showed that the flora was mainly the type of transition from tropical to temperate in the study area. Twenty-one rare species (those with individual number fewer than two in the plot) accounted for 31.82% of the species total. The distribution of rare species in Tianlongshan plot might be determined by multi-dimensional factors such as climate, topography, biogeographic processes, as well as anthropogenic disturbance. In the plot, the 13 species with Ⅳ≥1 contributed 88.81% to the Ⅳ of the community. The species with high Ⅳ are Lithocarpus confinis, Platycarya strobilacea Itea yunnanensis, Machilus cavaleriei, Carpinus pubescens, Pittosporum brevicalyx, Lindera communis, etc. The average DBH of all individuals in the plot was only 5.12 cm, and DBH size-class distribution followed a reverse "J" shape, indicating abundant regeneration. The spatial distribution of some dominant woody species showed obvious aggregation pattern in plot scales possibly related to high habitat heterogeneity in karst landscape. Monitoring and research on secondary forests in the north subtropical karst region will contribute to further understanding the mechanisms of biodiversity maintenance and community assembly in the process of vegetation restoration. Further studies should concentrate on the maintenance mechanisms of diversity and stability of forest community, the coupling relationships between above-ground and underground ecological processes, and the response and adaptation of vegetation to short-term disturbance events and long-term climate change in the north subtropical karst regions in southwest China.