Through sample plot harvesting and measured data, biomass, content, storage and spatial distribution of carbon in medicinal plants Eomecon chionantha Hance were investigated in Taojiang, Hunan province. Results showed the biomass of Eomecon chionantha Hance was 1744.70 kg/hm², and root biomass was 1278.63 kg/hm², which was highest and accounted for 73.9%. And the biomass ratio of underground (root) and aboveground (leaf and stem) was 2.74. The average carbon content was 450.54 g/kg for different organs of Eomecon chionantha Hance and decreased in the order leaf>stem>root. Carbon content ranged from 6.63 to 38.50 g/kg in the soils. Carbon content in 0-15cm depth was the highest, and it gradually decreased with the increase of soil depth. Carbon storage in ecosystem was 101.19 t/hm². Carbon stocks in the different components of the studied ecosystems were in an order as: soil >vegetation> litterfall.Carbon storage was 0.79 t/hm² in vegetation layer, which accounted for 0.78% in the whole ecosystem. In vegetation layer, carbon storage in underground root was 0.57 t/hm², which accounted for 72.2% and was the largest carbon pool in the vegetation layer。Carbon storage was 0.22 t/hm² in litter layer, which only accounted for 0.22% in the whole ecosystem. And litter layer was the main channel connecting plant aboveground and soil carbon pool. Most of carbon stored in soil in Eomecon chionantha Hance ecosystem, and soil carbon storage was 100.18 t/hm², which accounted for 99.0% in total carbon storage, and was the main carbon pool in Eomecon chionantha Hance ecosystem. The results will provide reference for further research on ecological functions of herbaceous plant in subtropical area.