Abstract: In this study the niche characteristics of important arbor species in Dayu Island, southeast China are analyzed with quadrate methods. The results showed that the diversity indexs of arbor species low, such as their Shannon-Wiener index 1.26, Margalef index 1.44, Simpson index 0.54 and Pielou index 0.57. The dominant species in the arbor layer was Acacia confusa, with important value of 53.84%. This was followed by Pinus massoniana, Eucalyptus citriodora and Litsea glutinosa. The analysis of niche characteristics indicated that the niche breadth of the Acacia confusa was the highest. The Levins niche breadth value was 19.00 and the Shannon niche breadth value was 2.84.Pinus massoniana, Litsea glutinosa and Eucalyptus citriodora also had larger niche breadth values. The highest niche overlap value of 0.673 was found between Acacia confusa and Pinus massoniana, followed by 0.633 between Acacia confusa and Litsea glutinosa. The DBH and crown diameter of Acacia confusa, Pinus massoniana, Eucalyptus citriodora and Litsea glutinosa were similar in their spatial distribution. In summary, the diversity index of arbor species in Dayu Island was low, the plant species were simple and the dominant species were relatively obvious. The plants with smaller niche characteristics had higher habitat requirements and the whole ecosystem was fragile.