Abstract: In the report， the betel nut plantation of three forest ages （young aged forest， middle aged forest， and mature forest） in Fengmu Forest Farm， Tunchang County， Hainan Province， were used as the research object， and the distribution characteristics of root carbon storage and soil organic carbon storage in the 0~100 cm soil layer in the underground part of a plantation were elucidated. The results indicated that in the 0~100 cm soil layer， the root system of betel nut plantation is mainly concentrated in the surface layer （0~30 cm）， and with the deepening of the soil layer，the root biomass decreases significantly， mature forest （1244.26 g·m^-3） > medium aged forest （993.26 g·m^-3） > young aged forest （658.59 g·m^-3）； with the growth of forest age， the change of the root carbon storage was as follows：mature forest （6.23 t·hm^-2） > middle aged forest （4.97 t·hm^-2） > young forest （3.57 t·hm^-2）. The distribution of soil organic carbon in the 0~100 cm soil layer of areca nut plantations with different stand ages showed that with the deepening of the soil layer， the content of soil organic carbon decrease significantly， there are differences among the soil organic carbon of the different forest ages， however， it is not significant. the organic carbon content of young forest is 2.64~21.65 g·kg^-1， the organic carbon content of middle-aged forest is 3.56~25.21 g·kg^-1， and the organic carbon content of mature forest is 4.37~31.77 g·kg^-1. There are significant differences among the soil carbon storage of the different forest ages， mature forest （125.72 t·hm^-2） > middle aged forest （107.58 t·hm^-2） > young forest （90.83 t·hm^-2）. There are the highly significant between the soil carbon storage and the organic carbon， total nitrogen， total phosphorus， pH， bulk density， saturated water content of the young Areca catechu forest （P<0.01）. There was significant difference between soil carbon storage and soil organic carbon in betel nut middle aged forest and mature forest （P<0.05）， but there was no significant difference with other indicators （P>0.05）. By comparing with the carbon reserves of main plantations in Tunchang area， the soil carbon reserves of the betel nut plantations are richer， and the carbon sink capacity of the betel nut plantations are higher， which can be used as the tree species for developing carbon sink.