Abstract: In order to explore the role of microbial biomass carbon (MBC) in ecosystem carbon cycle of Schima superb plantations in the sloping-land with purple soils in Hengyang. The time and space distribution dynamics of MBC in middle-aged plantation (MAP) and mature plantation (MP) was studied by using the chloroform fumigation extraction method. And the relationship between MBC and soil organic carbon (SOC) were also analyzed. The results showed that: (1) there was significant difference of MBC in MAP and MP in the month of 1-2, 3-4, 5-6, 7-8, 9-10 and 11-12 (P＜0.05), and there were 2 peaks in the whole year, the first peak value was at the month of 3-4, the second peak value was at the month of 9-10, MBC reached the minimum value at the month of 11-12; (2) There was also significant difference of MBC in MAP and MP in the soil layers of 0-20 cm, 20-40 cm, 40-60 cm, and the maximum was in the layer of 0-20 cm, the minimum in the layer of 40-60 cm, which exhibited a vertical distribution pattern; (3) The relationship between MBC and SOC was: y=21.654x+54.128 (R2=0.984, P＜0.01); (4) The MBC/SOC increased with increase of soil horizons showed SOC transferred gradually from the layer of 0-20 cm to the layer of 40-60 cm and soil C was in accumulated status, the results showed that the soils of MAP and MP were C pool.