To provide theoretical basis for restoration of black soil and tree species screening, the vertical distribution and its influencing factors of soil organic carbon and labile carbon fractions of converting cultivated lands into forestlands in typical black soil region were investigated. In the typical black soil area of Northeast China, three return farmland to forest land were selected as the research objects, and the afforestation trees were Populus×xiaohei, Pinus sylvestris var. mongolica and Larix gmelinii The research studied the vertical distribution characteristics of soil organic carbon, microbial biomass carbon, and dissolved organic carbon and their relationships with soil physicochemical properties and soil enzyme activities. The result showed that: The soil dissolved organic carbon content (1578.56 mg/kg) at 5-15 cm was significantly lower than that of larch (1936.98 mg/kg) and Pinus sylvestris (2046.07 mg/kg), The microbial carbon content (2151.53 mg/kg) was significantly higher than that of Populus ×xiaohei (1298.32 mg/kg) and larch (1164.75 mg/kg); The dissolved organic carbon content (1541.57 mg/kg) at 15-30 cm was significantly lower than that of larch (1957.04 mg/kg) and Pinus sylvestris (1881.31 mg/kg). The microbial carbon content (2256.99 mg/kg) was significantly higher than that of Populus×xiaohei (1708.50 mg/kg) and larch (1200.55 mg/kg).Soil pH, soil total phosphorus content, soil water content and soil bulk density were significantly different among different tree species. The contents of soil organic carbon and dissolved organic carbon decreased gradually with the increase of soil depth, and the content of microbial biomass carbon had no significant difference between different soil depths. Redundancy analysis and correlation analysis showed that soil dissolved organic carbon and microbial biomass carbon were positively correlated with soil phosphorus content, and soil organic carbon was positively correlated with soil nitrogen content, plant fine root biomass and β-1,4 glucosidase(BG). After returning farmland to forest, the soil organic carbon content of different tree species was not significantly different, but there were significant differences in soil dissolved organic carbon and soil microbial biomass and carbon content between different tree species. Soil total phosphorus content was the most important factor affecting the vertical distribution of soil organic carbon and soil microbial biomass carbon among the three tree species. Soil total phosphorus could explain 27.33% of the variation of soil organic carbon, soil dissolved organic carbon and soil microbial biomass carbon in the forest land of different tree species. The ratio of soil carbon to phosphorus could explain 24.37% of the variation of soil organic carbon, soil dissolved organic carbon and soil microbial biomass carbon in the forest land of different tree species.