The effect of drainage on soil dissolved organic carbon (DOC) in the Xiaoxing'an Mountain forests was investigated by selecting Larix gmelinii plantation wetlands of different ages (drain in 1974, drain in 1985, drain in 1992, and drain in 2003), as well as a natural forest swamp wetland (L. gmelinii marsh). The results showed that soil DOC content decreased vertically with soil depth for all sites. Compared with the natural forest wetland, the DOC content in all soil layers was lower (P<0.05). The soil organic carbon (SOC) content, DOC/SOC, and soil available nitrogen (N) in the surface layer (0-10 cm) of the natural forest swamp were all higher than those in the drained forests. In contrast, the available phosphorus (P) content was lower in the natural wetland than in the drained forests (P<0.05). In the soil surface (0-10 cm), the time since drainage was significantly negatively correlated with DOC, DOC/SOC, SOC, and soil N, and was significantly positively correlated with the available P (P<0.05). After drainage of the soil surface (0-10 cm), DOC and available N (ammonium nitrogen, nitrate nitrogen) were inversely proportional to the effective P (P<0.05). In the forest wetlands where drainage ditches were dug, the soil moisture status was changed to promote the forest growth. Overall, the area of the Xiaoxing'an Mountain forest wetlands covers 106.96 ten thousand ha, with great carbon sequestration potential. Its average carbon density was higher than natural forest carbon densities, as well as the carbon density of the forest vegetation in Heilongjiang Province. It therefore plays an important role in the regional carbon cycling. Since the 1970s, the wetlands in the Xiaoxing'an Mountain forests have been greatly influenced by human activities, and mainly by wetland drainage. Movement of soil DOC with wetland drainage occurred in the directions of the water movement. A portion of the soil DOC moved along the horizontal and vertical direction of the drainage ditches, or was lost directly to the water. At present, research on the impacts of human activities on DOC is mainly focused on how wetland reclamation for farmland changes DOC, as well as the effects of different land use patterns on soil DOC.In this study, we researched the forest swamps of the Xiaoxing'an Mountain forests. We conducted a quantitative study on the changes of soil DOC and SOC after drainage and transformation, in order to understand the role of DOC in the regional ecosystem's carbon cycle and the mechanisms of carbon transformation, in order to provide a theoretical basis for the management and sustainable development of the regional wetland ecosystems.