Studying the diversity and niche characteristics of herbaceous plants in different developmental stages of Tiankeng can better understand the response mechanism of the herbaceous layer to the environmental changes and provide an important scientific basis for the protection of ecological environment and biodiversity resources in Tiankeng. In this study, the herbaceous in different developmental stages of Tiankeng (the earlier stage, middle stage, and later stage) were selected as the objects. We used the method of space instead of time to establish 168 herbaceous quadrates in Dashiwei Tiankeng Group, Guangxi and carried out investigations. Shannon-Wiener index, Simpson index, Pielou's index and Patrick index were used to evaluate the herb diversity at different developmental stages of the Tiankeng. The ecological niche characteristics (niche width and niche overlap) of main species in the herb layer of the different developmental stages of Tiankeng were calculated. The results showed that:(1) a total of 98 species of herbaceous plants belonging to 71 genera and 34 families were recorded in Dashiwei Tiankeng Group, Guangxi. The principal families were Dryopteridaceae, Urticaceae, Pteridaceae, Asteraceae and Poaceae. (2) Pielou's index and Shannon-Wienner index of herbs in the later development stage of Tiankeng were significantly higher than those in the earlier development stage of Tiankeng (P<0.05), indicating that with the Tiankeng developed to the later stage, the number of species in the herb layer increased and the species distribution pattern was steady. (3) With the development of Tiankeng, the importance value of sciophiles in herb layer decreased, while the importance value of heliophiles and semishade increased and the dominance was prevalent in heliophiles than sciophiles. The herb layer would go through three ecotype transition processes of sciophiles-sciophiles and semishade-heliophiles. (4) The average value of niche similarity and niche overlap of dominant herbs at each developmental stage of Tiankeng were lower than 0.5, indicating that different developmental stages of Tiankeng had a slight impact on the niche of herbs. The herbaceous layer had obviously ecological differentiation and weakly inter-specific competition. (5) In the species pairs of dominant herbs large niche overlap and small relative height at each development stage, the species pairs of different ecological habits accounted for different proportions. The species pairs of the middle development stage of Tiankeng was much higher than that of earlier and later development stages of Tiankeng. The results showed that herbaceous plants with different ecological habits at different development stages had different competition degrees for light energy. The herbs in the middle development stage of Tiankeng had the fierce competition for light. In a word, the herb layer of Dashiwei Tiankeng Group in Guangxi was obviously differentiated, the community structure was relatively stable, and the species diversity of the later development stage of Tiankeng in herb layer was rich.