The seasonal tropical rainforests in karst regions of southwestern China are well known for their high biodiversity and rich array of endemic species. However, changes in the woody floristic composition and diversity during forest succession remain unclear. In this study, we used the space-for-time substitution method to analyse the floristic composition and diversity of woody plants across three successional stages (young secondary forests, old secondary forests and primary forests). Our results indicated significant differences in species composition among the various successional stages, with species richness peaking in the old secondary forests. Additionally, as succession progresses, the proportion of the relative importance values of dominant species in the community gradually decreases compared to the total importance values. In the β-diversity, the species richness, Simpson index and Shannon–Wiener index all reached an apex in the old secondary forest, whereas the Pielou evenness index gradually increased over time, reaching its maximum in the PF. The β-diversity analysis suggested that species turnover occurred during succession, with no significant similarity between communities at different stages. This study demonstrated that the floristic composition and diversity of woody plants underwent continuous changes as succession progressed in karst forests. Anthropogenic disturbances and competitive exclusion may co-regulate the floristic composition and diversity at different forest stages in mountainous karst areas.