Abstract:[Objective] To investigate the distribution of soil organic carbon(SOC) and total nitrogen(TN) in different positions of semi-fixed dune in Horqin sandy land, for exploring the vegetation succession mechanism of different dune slope positions.[Methods] Soil samples were collected from the bottom of windward slope, mid-slope, top and leeward of semi-fixed dunes with 5 m height, along the direction of prevailing wind. Soil bulk density, SOC and TN contents were measured and then the ratio of carbon/nitrogen(C/N), densities and stocks of SOC and TN were calculated.[Results] (1) SOC contents in all 4 positions of the semi-fixed dune were decreased with soil depth and the obvious variation occurred in depth of 0-40 cm, and there were position differences (p<0.05) of SOC contents at depth of 30-40 cm and 60-100 cm; (2) TN contents and bulk density were all insignificantly different among different depths and slope positions. Ratio of C/N showed significant differences between the bottom and top of semi-fixed dunes. The ratio at the depth in leeward from 60 to 100 cm had significantly higher values than others; (3) SOC density decreased significantly with soil depth in all slope positions, and there existed significant differences of SOC density at depth of 30-40 cm among slope positions. No significant differences of nitrogen density were found among dune positions and profile depths; (4) Stocks of SOC and TN were 716.89 and 94.14 kg/m2 in semi-fixed dune, respectively. The differences among slope positions were insignificant. However, contribution in each layer of SOC stock to the total stock was different between slope positions while TN was similar in each layer to the total.[Conclusion] There were insignificant differences in both contents and densities of SOC and soil nitrogen in semi-fixed dune of Horqin sandy land among dune position, however, contents of SOC and soil nitrogen differed significantly among soil depth in all dune positions, especially at the depth of 30-40 cm, which changed intensely, and this may due to plant root distribution of this depth.