To explore the community characteristics and diversity of Pinus thunbergii community, scientifically manage P. thunbergii shelterbelt and protect the diversity of P. thunbergii community, we investigated the species composition, flora, and community type of the P. thunbergii community with the quadrat method in eight affiliated islands of Pingtan from 2018 to 2020, and analyzed the relationship between the diversity indexes and environmental factors by redundancy analysis. The results showed that: (1) There were 138 species of vascular plants belonging to 117 genera and 54 families in the study area, with few gymnosperms and ferns in total. (2) Phanerophytes (68 species) and therophytes (30 species) were high in the life form. In terms of growth form, there were 8 species of arbors, 39 species of shrubs, 76 species of herbs, and 15 species of vines, with more species of herbs and shrubs than arbors. (3) Both families and genera had the characteristics of tropical traits but lack Chinese endemic distribution. (4) Group average clustering method was used to divide the vegetation in the research area, which consisted of three formation types and nine association types. (5) In the comparison of the overall diversity of the community, Pinus thunbergii + Acacia confusa plant formation was higher than the Pinus thunbergii + Eurya emarginata plant formation and Pinus thunbergii plant formation. The diversity indexes in the herb layer and shrub layer of each plant community were all higher than that in the tree layer. (6) The redundancy analysis showed that the soil total phosphorus, soil total potassium and slope aspect had significant effects on the diversity