The spatial distribution in karst areas is uneven and the soil is shallow, resulting in different niche with varying soil thickness. Soil serves as the substrate for plant growth, and soil thickness affects nutrient availability, plant development, and community characteristics. It focuses on grassland communities in karst areas to explore the characteristics of plant communities and species diversity in habitats with different soil thicknesses. The results show that：1) Plant species growth varies among different habitats; as soil thickness increases, Crassulaceae and Poaceae decrease gradually while Fabaceae and Rosaceae increase significantly, indicating a more dominant position for Asteraceae plants. 2) Species diversity of communities is higher in habitats with moderate soil thickness (shallow-medium soils, medium-deep soils), suggesting that moderate soil thickness is more favorable for the development of plant species and diversity. 3) As habitat soil thickness deepens, dominant species become increasingly stable within the community, showing a trend from herbaceous plants to woody plants in terms of composition. In conclusion, in karst regions, suitable habitat conditions combined with ecological niche complementarity make moderately thick soils richer in plant species diversity which promotes symbiosis among plants to facilitate community succession.