THE stable carbon isotopic composition of soil organic carbon is a powerful tool for discussing the source ofsoil CO_2 and the relationship of CO_2 source and sink between soil CO_2 and atmosphere CO_2 and has beenwidely studied. However, few similar researches have been done in karst area which comprises 15%global terrestrial area. Preliminary research results about the stable carbon isotopic composition of soil organic carbon in karst area are reported here. In April and August 1998, the samples were collected continuously at 5-cm intervals from 0 to -45cm depth in meadow soil profile described by Zheng and located in the Hongfong Lake area in the central Guizhou Plateau which lies in the central East-Asia karst area. CO_2 for δ~(13) C analysis was prepared by THE stable carbon isotopic composition of soil organic carbon is a for tool for discussing the source of so CO_2 and the relationship of CO_2 source and sink between soil CO_2 and atmosphere CO_2 and has been studied fully. However, few similar researches have been done in karst area which Preliminary research results about the stable carbon isotopic composition of soil organic carbon in karst area are reported here. In April and August 1998, the samples were collected continuously at 5-cm intervals from 0 to -45 cm depth in meadow soil profile described by Zheng and located in the Hongfong Lake area in the central Guizhou Plateau which lies in the central East-Asia karst area. CO_2 for δ ~ (13) C analysis was prepared by