Abstract: The BIOLOG ECO-plate method was used to study the response of soil microbial functional diversity to ecological succession in karst area.In the study area, four different community succession stages were selected to study the microbial function diversity of soil, i.e., virgin arbor-forests, secondary arbor-shrub mixed forests, shrub, and grass-land, and a non-karst forests plot was selected as a control.The results show that, with the ecological succession of arbor-forest to shrub process, the microbial activity exhibits gradual decreasing tendency.The functional diversity is sensitive to response to the ecological succession.Soil microbes show higher activity and richness in karst areas than in non-karst areas, but the community uniformity is lower and the structure is more unstable.Principal component analysis shows that the succession causes significant differentiation of the metabolic patterns of microorganisms, and the carbon sources that play a major role in differentiation are sugars, carboxylic acids and polymers.According to the average well color development (AWCD) and principal component analysis, the authors hold that larger environmental changes may cause the soil microorganisms to adopt the r strategistis when the succession progresses to the grass slope stage.According to the change of soil microbial functional diversity during the reverse succession, the shrub stage can be regarded as the threshold of the entire succession stage of the karst ecosystem.