The depolymerization of soil organic nitrogen (SON) depolymerases on soil macromolecule organic nitrogen is the rate-limiting step of the soil nitrogen cycle, which plays a crucial role in the soil nitrogen cycle. However, the dynamics of SON depolymerase activities and their influencing factors in subtropical forests at middle and high altitudes are still unclear. In this study, the soil environmental factors, physicochemical properties and the activities of eight kinds of SON depolymerases were measured in the Pinus taiwanensis forest at the altitude of 1200-2000 m in Wuyishan Nature Reserve, and we investigated the distribution of SON depolymerase activities and their influencing factors at different altitude gradients. The results showed that the significant differences were found in all soil environmental factors and physicochemical properties measured at different altitudes except DON content. The activities of SON depolymerase displayed different distribution patterns with altitude gradient:alkaline protease (ALPT), neutral protease (NPT), laccase (Lac) and leucine aminopeptidase (LAP) increased significantly with altitude, and acid protease (ACPT), chitinase (Chi) exhibited a trend of increasing first and then decreasing, while manganese peroxidase (Mnp) and glutaminase (GLS) decreased significantly at altitude of 1800 m. Redundancy analysis showed that SON depolymerase activities were obviously clustered at different altitudes, and the explanation degree of soil environmental factors and physicochemical properties to them was as high as 88.18%. Soil temperature (ST), soil moisture (SM), microbial biomass carbon (MBC), and mineral nitrogen (NH₄⁺, NO₃^-) are important predictors of SON depolymerase activities at different altitudes. Correlation analysis showed that most of SON depolymerase activities were negatively correlated with soil ST, while positively correlated with pH, SM, TN, MBC, NH₄⁺ and NO₃^-. The dynamics of NH₄⁺ and NO₃^- showed a wave-like fluctuation with altitude gradient. Compared with the upstream organic substrate, the mineral nitrogen in the downstream inorganic nitrogen cycle had a more direct impact on SON depolymerase activities. This study is helpful to broaden our understanding of the mechanism of soil nitrogen cycle in subtropical forests at middle and high altitudes, and is of great significance to the protection of soil available nitrogen and the maintenance of soil productivity.