Abstract: Using indigenous tree species to transform large area pure plantations has been an effective closetonature forest management mode in China islands. By using the biomass allometric equation and combined with the investigation data from sampling plots, the carbon storage of the dominant species Pinus thunbergii and Robinia pseudoacacia in the plantations on the Nanchangshan Island of Miaodao Archipelago in Changdao County of Shandong Province was estimated．The average carbon storage in the arbor layer of P. thunbergii and R. pseudoacacia plantations was 56.81  and 37.26 t·hm^-2, respectively, being higher than the  average carbon stock (27.62 t·hm^-2） of tree plantations in Shandong Province. Slope aspect and stand density were the important environmental and biological factors affecting the tree’s carbon stock in the Island, respectively. There was no significant correlation between the average cumulative rate of biomass in the arbor layer of P. thunbergi plantation and the stand age. The P. thunbergii with good carbon sequestration function could be an ideal tree species on Nanchangshan Island.