Vegetation naturalness evaluation is an important theoretical basis of forest natural restoration. Due to the special geographical environment, islands vegetation is different from the mainland in structure and function. However, there is few studies on the island vegetation naturalness evaluation that combined plant functional trait. Based on the vegetation information, soil properties, and diversity characteristics (species and functional diversity) across 74 plant communities of 10 typical islands in eastern China. Thirteen indices with middle and high sensitivity of vegetation naturalness were selected, then the evaluation index system of island vegetation naturalness was constructed by using the analytic hierarchy process. The comprehensive index of vegetation naturalness was calculated and the levels of vegetation naturalness were divided for each island. Our results showed that the weights of vegetation naturalness indexes in the comprehensive evaluation system were vegetation information > diversity characteristics > soil properties, among which the best indexes are plant natural compose index, soil water content, plant Shannon-Weiner index, and Rao's index. Across 10 islands, the degree of vegetation naturalness was the highest on Da jinshan Island (0.611), representing the semi-natural forest, and the lowest in North Changshan Island (0.345), reflecting the semi-plantation. Among the climatic zones, the degree of vegetation naturalness was relatively lower in the islands of the warm temperate and southern subtropical regions than in those in the middle-subtropical region. The results not only used common indexes of mainland vegetation evaluation, but also combined plant functional diversity, which will help to provide quantitative evidence for the ecological status of island vegetation in eastern China, and also provides support for the island vegetation conservation management and natural restoration.