Acacia confusa is widely distributed in tropical and subtropical coastal regions and plays a significant role in island ecosystems. This article took the Acacia confusa Plantation Foreston six islands in the Eastern Fujian area as the research object. To analyze the impacts of environmental factors on species diversity and functional diversity within the communities, as well as the relationships among them, this study employed correlation analysis, redundancy analysis, multiple stepwise regression analyses and structural equation modeling based on community surveys. The results showed that: 1. The Shannon-Wiener diversity index (H) of species on Culu Island and the Pielou evenness index (J) of species on Langqi Island were significantly lower than those on other islands. There was no significant difference between Simpson's diversity index (D) and Patrick's richness index (R), but significant differences in the four functional diversity indices among the six islands. 2. The functional richness index (FRic) exhibited a significant positive correlation with four species diversity indices; the Rao's quadratic entropy index (RaoQ) showed significant negative correlations with the Shannon diversity index (H), Simpson diversity index (D), and Patrick richness index (R) of species. Additionally, there was a significant negative correlation between the functional divergence index (FDiv) and the Pielou's evenness index (J). Except for the functional richness index (FRic), the fitting correlations between the other functional diversity indices and the species diversity indices were all relatively weak. 3.Redundancy analysis indicated that six environmental factors-soil total nitrogen, soil total phosphorus, altitude, slope aspect, crown density, and wind speed-had significant impacts on species diversity indices (P< 0.05); five environmental factors, including soil total potassium, total content of water-soluble salts, altitude, crown density, and distance from the coastline, significantly influenced functional diversity indices (P<0.05). 4. The structural equation model revealed that soil factors such as pH and total potassium are significant factors influencing species diversity and functional diversity in communities. Crown density is a crucial factor affecting community diversity, with direct effects outweighing indirect effects. Mean annual precipitation directly affects species diversity, while its impact on functional diversity is indirectly mediated through crown density and soil total potassium. In summary, there are significant differences in the species diversity and functional diversity of Acacia confusa communities on different islands in the Eastern Fujian area, which are jointly influenced by soil, topography, and climate factors. This study provides theoretical support for the construction of island plantations and the conservation of biodiversity.