Studying the coupling relationship between plant community functional diversity and species diversity and the response mechanism to environmental heterogeneity in karst is of great significance for revealing the maintenance mechanism of the function and structure of karst ecosystems. Five functional diversity indices and four species diversity indices were calculated for the karst secondary communities in central Guizhou.The coupling relationship between functional diversity and species diversity was investigated by regression fitting,and the effects of environmental factors on functional diversity were investigated by RDA redundancy analysis. The results showed as follows: (1) The functional diversity index of FRic, FDis and RaoQ in the tree layer was significantly higher than that in the shrub layer in the middle Guizhou Karst secondary forest; (2) The coupling relationship between functional diversity and species diversity was significantly different. There was a significant S-type positive relationship between FRic, Margale and Shannon in tree layer, and a significant positive fitting relationship between FDis, RaoQ and species diversity index. The significant regression relationship between species diversity and functional diversity in shrub layer was weak, and only Margale, Shannon and FRic had significant positive fitting relationship. (3) Soil thickness (SD) and soil moisture content (SMC) determined the functional diversity of tree layer, while slope (SLO) and rock exposure rate (RER) determined the functional diversity of shrub layer. The results showed that the tree layer played a greater role in ecosystem function and structural stability than the shrub layer in the middle and late stages of succession in central Guizhou. The relationship between community functional diversity and species diversity was positive, and the functional diversity at different levels of the community had different responses to heterogeneous mountain habitats,which jointly determined the ecosystem function of the community.