A tract of farmland on a typical mount in Northeast China was selected as a case to study effect of soil erosion and deposition on dynamics of soil organic carbon (SOC) by determining some properties and δ¹³C of the soils at different topographic positions.The results showed that the δ¹³C value of the surface soil was significantly correlated to slope gradient, clay content, soil moisture and pH.The change in δ¹³C with depth in soil profile reflected input of plant residue and accumulation of eroded soil, which helps to identify buried soil surfaces.The slope (β) of linear regression between isotopic composition and SOC concentration was positively related to slope gradient of the landscape and negatively related to clay content, indicating that β could be used as a useful index to describe mineralization of SOC at the erosion position.The contents of C₃-C at the shoulder and back of the slope were significantly less than that at the summit and C₄-C showed no obvious difference between them, indicating the differences in SOC content between erosion sites resulted from C₃-C.The contents of C₄-C at the foot and toe of the slope were significantly less than those at the shoulder and back of the slope, which indicates that the loss of new carbon at deposited sites was greater.