The construction of plantantion forest in island is conducive to weakening and eliminating the ecological vulnerability of the island. However, there are many shortcomings in the currently single plantation forest community structure, and the selected vegetation also has the problem of not adapting to the island environment. In this study, the vegetation types, species composition, plant functional traits, and species diversity of Pinus massoniana semi-natural forests in six islands of Sandu Gulf of Ningde were analyzed by sample method, and the correlation between species diversity and environmental factors was analyzed by redundancy analysis(RDA). The aim is to understand the succession status, community structure characteristics, species composition, and the correlation between species diversity and environmental factors, enrich the basic data of local vegetation, and provide a theoretical basis for the construction of island plantation, vegetation restoration selection, and rational management of local Pinus massoniana forests. The results showed that: (1) a total of 255 species (including 5 varieties) of vascular plants belonging to 168 genera and 86 families were recorded in 40 quadrats. In the life form spectrum, arbor and shrub species were the most, accounting for 37.25% and 30.20% of the total number of species, respectively. Phanerophytes accounted for a significant proportion, accounting for 83.92%. The light tolerance of neutral plants was dominant, accounting for 69.02%. (2) The vegetation in the study area was divided into 5 groups and 33 associations by group average clustering method, which belonged to 2 vegetation types of evergreen coniferous and broad-leaved mixed forest and evergreen coniferous forest. (3) The diversity index of evergreen coniferous and broad-leaved mixed forest was significantly (P<0.05) higher than that of evergreen coniferous forest, but the diversity index of shrub layer in Pinus massoniana +Adinandra millettii forest was significantly lower due to the influence of canopy density. (4) Shrub layer was the dominant layer in Pinus massoniana forest, and the diversity index (except Pielou index) was significantly (P<0.05) higher than that of arbor layer and herb layer. The herbaceous layer was affected by allelopathy of Dicranopteris pedata, and the diversity index was obviously lower. (5) The results of redundancy analysis showed that soil pH and available potassium significantly (P<0.05) affected the species diversity index of the community. The two soil factors accounted for 27.6% of the species diversity, but there were 72.4% unknown factors. (6) There was a significant (P<0.05) quadratic function relationship between the importance value of Schefflera octophylla in shrub layer and crown density.