Abstract: Soil cores were collected from a 28.5 hm² slope farmland in the black soil region of Northeast China. Based on the sampled data of ¹³⁷Cs, ^210Pb_ex and SOC, the potentials of applying ¹³⁷Cs and ²¹⁰Pb_ex for assessing SOC redistribution were evaluated, aimed to approach the impact of soil erosion on soil organic carbon (SOC) in black soil region. At both planar and vertical directions, the ¹³⁷Cs,²¹⁰Pb_ex and SOC in the farmland had similar distribution patterns. Although there were large planar variations in the ¹³⁷Cs and ²¹⁰Pb_ex areal activities and the SOC stock as affected by soil erosion and deposition, the ¹³⁷Cs, ²¹⁰Pb_ex and SOC had similar changing trends over the landscape. Two depth distribution profiles were also used to  study the relations of 137Cs and 210Pbex with SOC. At eroded site, the radioactivities of ¹³⁷Cs and ^210Pb_ex and the SOC mass fraction did not show large variations in 0-25 cm soil layer, but decreased sharply below 25 cm. For the deposition sample, the radioactivities of ¹³⁷Cs and ²¹⁰Pb_ex in 0-100 cm soil increased firstly and then decreased. The SOC mass fraction also had similar depth distribution pattern in this soil layer. The ¹³⁷Cs and ^210Pb_ex presented positive linear correlations with the SOC, indicating that ¹³⁷Cs, ²¹⁰Pb_ex and SOC moved with the same physical mechanism in the farmland, and fallout ¹³⁷Cs and ^210Pb_ex could be used to study spatiotemporal distribution characteristics of SOC in the black soil region under the condition of soil erosion.