Soil carbon sequestration of sand-fixation plantation and the response of soil respiration to different water condition in Pinus sylvestris var. Mongolica woodland and mobile sand dune were investigated in Horqin Sandy Land. Results show that (1) after 23 years since Pinus sylvestris var. Mongolica was planted in mobile sand dune, the content of very fine sand and silt+clay increased significantly in soil, whereas soil bulk density decreased; (2) the soil organic carbon sequestration in woodland was 221.8 g·m-2and 113.9 g·m-2 at the depth of 0~5 cm and 5~15 cm, respectively, and the sequestration rate was 9.64 g·m-2 and 4.95 g·m-2·a-1, respectively; the CaCO3-C sequestration was 4.0 g·m-2 and 2.5 g·m-2 and the rate was 0.17 g·m-2 and 0.11 g·m-2·a-1, respectively; (3) during drought period, soil respiration showed a strong negative exponential relationship with air temperature; soil respiration in woodland was higher than that in mobile sand dune whether the condition is drought or not; and (4) soil respiration increased after rain process, but the increment was higher in woodland; the removal of surface litter resulted in decrease of soil respiration and rain exacerbated the difference.