Abstract:A field survey was carried out in the Liuxing Tiankeng of Leye, Guangxi, to collect plant community data. Sampling plots were set up using quadrat method at the middle and the bottom of Liuxing Tiankeng for the census of canopy trees and understory plant community. Species composition, community structure, and diversity were analyzed using quantitative ecology methods and the specieshabitat association was explored. The results are as follows, (1) 60 canopy trees with a diameter at breast height (DBH) = 10 cm were found from the sampling plot, which belonged to 13 families, 17 genera, and 18 species, and the stem density was ≈188 plant/hm2. In the understory layer, 94 plant individuals of 43 species from 28 families and 38 genera were recorded, and the stem density was 23 500 plant/hm2. The species diversity in the community was rich, and ShannonWiener diversity index and evenness index was relative high. The family and genericlevel diversity of canopy trees was very high, reflecting the ancient and isolated nature in the community composition. (2) The dominant family was Lauraceae in Liuxing Tiankeng, which consisted of 4 species and 14 individuals in the canopy layer; while in the understory, it comprised 3 species and 7 individuals, of which 2 species were shared by the canopy layer. Families dominant in the understory layer with rich species were Euphorbiaceae (4 species), Compositae (3 species), Pteridaceae (3 species), and Dryopteridaceae (3 species). However, the specieslevel dominance was not obvious in the Tiankeng plant community. (3) The plant community in the understory layer encompassed various growth forms, with the majority of shrubs, the least of graminoids, and the less abundant tree seedlings, reflecting that the habitat in Liuxing Tiankeng provided abundant resource niches, and that the trees could not regenerate well with seedlings and saplings. (4) A high percentage of large trees existed in Liuxing Tiankeng. Of the 60 trees recorded, tree DBH ranged from 17.0 cm to 104.0 cm, with 34 trees having > 30 cm DBH, accounting for 56.6% of all the trees. These findings showed that Tiankeng forest community was primitive and free from human disturbance. (5) Twoway indicator species analysis (TWINSPAN) showed that plant community in the understory layer was more sensitive in response to habitat heterogeneity. However, none of the existing distribution in the canopy and understory layer could entirely separate the habitats at the middle and the bottom of Liuxing Tiankeng. These results will provide the baseline data and theoretical basis for further research on the occurrence, succession, and ecological adaptation of the plant communities in the karst Tiankengs with such special habitats.