[Objective] The relationship between soil particle size and organic carbon under different grassland use patterns was studied, to reveal the loss rate of soil organic carbon in grassland degradation process, in order to provide a scientific basis for the restoration and control of ecological environment in Horqin sandy land.[Methods] Taking the flow and semi-fixed aeolian sandy soil in the Wulijimulun River basin of Horqin sandy land as the research object, the relationship between grain size and organic carbon content was studied under different grassland utilization modes, such as the enclosed grassland in the basin, the salinization plots with different degrees of degradation and the artificially planted pasture plots.[Results] The enclosing measures played a significant role in controlling soil erosion and increasing soil organic carbon content. In the 0-20 cm soil layer of the watershed, the grain size composition was dominated by silt and sand. Due to the factors of tillage, the surface soil in oat and alfalfa plotswas coarser, and had higher peak and median grain size than other plots. In the study area, the particles with a size around 100 μm were easily to be eroded. For the soil particles with a size less than 100 μm, the organic carbon would be lost by 0.120 4 g/kg for every 1% wind erosion.[Conclusion] The saline-alkaline meadow land distributed in the hills can be combined with the enclosure measures and planting grasses, to prevent soil erosion and effectively increase the organic carbon content.