Soil organic carbon (SOC) is an important component of the global carbon cycle and has direct effects on the global carbon balance. The objectives of this study were to determine the effects of Silver-grass and Vetiver grass on soil carbon pool in natural environmental conditions. The results showed that: The photosynthetic rate of Vetiver grass was lower than Silver-grass. The biomass of Silver-grass was larger than Vetiver, and the maximum dry weight was 1966g•pot^(-1)•year^(-1) 3.67 times higher than Vetiver grass. The values of SOC, δ^13C and C % in different depth of the soil from Silver- grass-planted were significantly higher than that from Vetiver-planted soil. Which indicated that the ability of Silver-grass root-derived carbon (C) input into the soil was better than Vetiver grass. The δ^13C values in shoot of Silver-grass and Vetiver grass were -13.75‰ and -13.4‰, indicated that Silver-grass and Vetiver grass were both high in photosynthetic efficiency. The C﹪values of soil planted Silver-grass and Vetiver grass were higher than rice, corn and elephant-grass in traditional cultivation system. Hence, silver-grass and vetiver grass have been proved to be the ultimate grass species for soil and water conservation, Biomass Feedstock, ecologic environment improvement and SOC storage.