Investigating the primary factors of soil organic carbon (SOC) is important to elucidating the recovery mechanisms of soil organic carbon in degraded soils. A case study in Xingguo County of Jiangxi Province was conducted to assess the effects of soil type and parent material on soil organic carbon of forests in the eroded region. The results showed that significant differences were found in SOC content within soil types and parent materials, respectively. In general, yellow-red soils contained a markedly larger SOC content than red soils in all soil layers. SOC content on phyllite was considerably more than that developed on red sandstone and granite. Meanwhile, as for the contribution to the variability of SOC content, soil type explained over 30% of the variability of SOC content while parent material explained approximately 17% in the surface soil layer 0-20 cm, therefore, soil type played a more important role than parent material on SOC in the surface soil layers. However, in the 20-30 cm soil layer, the independent contributions of parent material and soil type to SOC content variability were roughly equal, respectively with 28.8% and 27.5%, which indicated that both parent material and soil type were considered as the main controlling factor in subsurface soil layers. Hence, the effects of soil type and parent material on SOC should not be neglected in the severely eroded region, and different water and soil conservation measures implementation in different regions can be benefit for soil carbon restoration of degraded soils.