Abstract：Root competition experiment in three woody species was carried out in six plots，each of them was 12.4 m × 10 m on Nan-ao Island situated on the east of Guangdong Province near Shantou city． The experiment site was in the community dominated by Eucalyptus robusta．The seedlings of Eucalyptus urophylla，A cacia auriculaeformis and Schima superba were respectively planted in 3 plots and another 3 with trenches around the plots so as to prevent roots from other plants． The growth rate， biomass and root competition intensity for the seedlings of 3 species were measured after the seedlings had grown for 165 days to 640 days．Th e results indicated that the biomass increment and growt h rate of all the seedlings un der root competition were lower than those of seedlings grown in plots with trenches．The influence of un derground root competition on the seedling growth was gradually decreased with the growt h of seedling age， and was then stable when reached to a certain stage． Root competition intensity ofthe seedlings ofS．superba，E.urophylla and A.auriculaeformis were 0.22，0.19 and 0.13 respectively．It was shown that seedling growth of exotic trees E.urophylla and A．auriculaeformis had more adaptation to root competition than that of native tree species S.superb