A study was conducted to investigate the distribution of total soil organic carbon,soil microbial biomass carbon and organic carbon in different size soil aggregates in three typical grasslands that were dominated by Panicum virgatum,Bothriochia ischaemum,Stipa bungeana in hilly-gully region on the Loess Plateau.The results showed that total soil organic carbon,soil microbial biomass carbon and organic carbon content in soil aggregates was higher in the soil surface than in other layers.The organic carbon contents of different grasslands in a descending order were Panicum virgatumBothriochia ischaemumStipa bungeana.A clear relationship was found between the organic carbon contents and the sizes of soil aggregates.2-1 mm aggregates had the highest soil carbon content.The total organic carbon content and organic carbon content in soil aggregates in Panicum virgatum grassland were higher than those in Bothriochia ischaemum grassland and Stipa bungeana grassland,while the microbial biomass carbon content was lower than that in Bothriochia ischaemum but higher than that in Stipa bungeana grassland.