A typical rolling farmland in the Black Soil region of Northeast China was selected in a case study to analyze impact of soil erosion and deposition on the loss, transportation and accumulation of soil organic carbon (SOC) in topsoil by measuring particulate organic carbon (POC), composition of water stable aggregates of different sizes and contents of associated carbon in different slope positions. Results showed that the contents of macro-aggregates, incorporated organic carbon (IOC) and micro-aggregate associated carbon at the shoulder-slope with serious erosion were 23%, 17.5% and 8.7％ lower than those of summit with weak erosion, respectively, while there was no significant difference in POC among three erosion sites. At foot-slope, a long-term soil deposition recipient, the contents of POC, macro-aggregates and macro-aggregate associated carbon were 56.1％, 47.9% and 67％ lower than those of summit, while IOC and micro-aggregate associated carbon were 10% and 18.7% higher than those of summit, respectively. The findings suggest that soil erosion and cultivation tend to break down macro-aggregates, whose content light in weight and fine in particle size are hence easily lost and transported with surface water flow, which in addition to the dilution function of subsurface soil leads to decrease in SOC content at erosion sites. Moreover, the fraction of light labile organic carbon is apt to be exploited and decomposed by soil microbes in the process of transportation and accumulation. As a result, SOC in the depositional sites was dominated by IOC and micro-aggregate associated carbon, forming a big passive carbon pool in the topsoil.