Soil carbon pool is the largest carbon pool in the terrestrial ecosystem. Previous studies mainly focused on the modern surface soil carbon pool, while research on the characteristics of ancient soil carbon pool is relatively limited. In this paper, taking the paleosol as the research object in the Xiaoluanhe watershed on Bashang plateau, Hebei Province, the characteristics of paleosol carbon pool of sparse grassland unit in an aeolian sandy layer and grass mixed ground unit in residual accumulation of rivers and lakes were analyzed by means of Optically Stimulated Luminescence (OSL) chronology, elemental geochemistry and aggregation classification method. The results show that the ages of paleosol in the study area were 5. 7~3. 3 ka in the Holocene geological period with warm and humid climate and adequate rainfall. The main species of coniferous forest- steppe vegetation were Pinus and Artemisia. The carbon pool was formed mainly by organic carbon (SOC), with an average SOC density of 3. 85 kg/m2, and the SOC storage of 153. 1×107 kg. The micro- aggregate content of river and lake sediments is higher, and provides strong physical protection to the carbon pool of paleosol layer, leading to higher stability of the carbon pool. However, the micro- aggregate content of aeolian sand layer sediment is relatively lower, and the physical protection provided to the carbon pool is weaker, which will accelerate the decomposition of organic carbon to a certain extent and decrease the stability of carbon pool. Different ways of protection and utilization should be adopted based on different origins in the Quaternary coverage areas, which will reduce the decomposition and loss of soil organic carbon. It is of great significance to promote local carbon storage and carbon neutralization work.