Abstract: Taking the natural oak forests in five forest farms in Hunan Province as the research objects, and based on field survey data from 50 standard sample plots, this study used species richness to measure diversity and employed principal component analysis, redundancy analysis, and hierarchical partitioning analysis to explore the relationships between shrub-herb species diversity and environmental factors. The results showed that a total of 81 shrub-herb plant species were recorded in the survey area, belonging to 47 families and 74 genera. Among these, 35 were shrub species and 46 were herbaceous species. The dominant families were Rosaceae, Theaceae, Ericaceae, Poaceae, and Fabaceae, and herbaceous species diversity was higher than that of shrubs. Soil was the dominant factor influencing shrub-herb species diversity, with soil moisture content serving as the core factor, exerting a significant positive effect on shrub-herb species diversity. The effects of environmental factors on shrub-herb species diversity differed between growth forms: herbaceous species were co-regulated by soil properties and temperature variation, whereas shrub species were more sensitive to moisture conditions. Therefore, it is recommended that in the management of subtropical natural oak forests, stand structure should be regulated to maintain relatively high understory soil moisture, thereby mitigating the potential threats of climate change to understory biodiversity.