We selected four adjacent plant communities with almost the same habitat conditions in Changsha County, Hunan Province, China. The four vegetation communities were composed of Loropetalum chinense-Vaccinium bracteatum-Rhododendron simsii scrub-grass-land (LVR), L. chinense-Cunninghamia lanceolata-Quercus fabri shrubbery (LCQ), Pinus massoniana-Lithocarpus glaber-L. chinense coniferous-broad leaved mixed forest (PLL), L. glaber-Cleyera japonica-Cyclobalanopsis glauca evergreen broad-leaved forest (LAG) to represent the secondary forest successional sequence in this region. Fixed sample plots were set up, and soil samples (0-40 cm) were collected and divided into four layers (0-10, 10-20, 20-30 and 30-40 cm). The contents and density of soil soluble organic nitrogen (SON), ammonium nitrogen (NH₄⁺—N) and nitrate nitrogen (NO₃^-—N) were determined, and the correlations between the contents of SON, NH₄⁺—N and NO₃^-—N and soil clay percentage, total nitrogen (TN), organic carbon (SOC) and microbial biomass were analyzed. The results showed that the contents of SON and NH₄⁺—N in each soil layer increased with the vegetation restoration. Compared with LVR, contents of SON in 0-40 cm soil layers in LAG, PLL and LCQ increased respectively by 225.78%, 121.22% and 54.73%, while contents of NH₄⁺—N increased respectively by 22.10%, 14.74%, and 7.80%. The contents of NO₃^-—N in each soil layer decreased first and then increased with the vegetation restoration. The NO₃^-—N contents in each soil layer of LAG were the highest, while LCQ was the lowest. The densities of SON and NH₄⁺—N in the 0-40 cm soil layer were 143.82~528.12 kg/hm² and 55.73~65.57 kg/hm² respectively. Compared with LVR, the densities of SON in LAG, PLL and LCQ increased by 267.20%, 98.40%, and 86.30%, while NH₄⁺—N increased by 17.70%, 7.90%, and 11.60%, respectively. The densities of NO₃^-—N in 0-40 cm soil layer was 22.91~25.87 kg/hm². Compared with LVR, LAG increased by 13.16%. The growth rates of SON and NH₄⁺—N densities between different stages showed the characteristics of fast-slowly-fast, while that of NO₃^-—N showed the characteristics of slow-slowly-fast. The effects of soil physicochemical properties and microbial biomass on SON and NH₄⁺—N were greater than that of NO₃^-—N. In conclusion, the vegetation restoration was conducive to the accumulation of soil N, improved the contents and densities of soil soluble nitrogen components and increased soil available N.