Three nitrogen application treatments viz. control (CK), low nitrogen(LN，N 40 kg/(hm²·a))and high nitrogen(HN，N 80 kg/(hm²·a))were set in a natural Castanopsis carlesii forest in the Castanopsis kawakii conservation area in Fujian Province, the changes of soil physicochemical properties, enzyme activities and their stoichiometric ratios under different nitrogen application years (4 years and 8 years) and different soil depths (0–10 cm and 10–20 cm) were studied to explore whether long-term nitrogen deposition aggravates soil phosphorus limitation in the subtropical areas. The results showed that:1) soil pH decreased after different years of nitrogen application, and soil dissolved organic nitrogen (DON) content in the 0–10 cm soil increased with the increase of nitrogen application. The content of microbial biomass nitrogen (MBN) decreased significantly in the 0–10 cm soil layer but increased significantly in the 10–20 cm soil layer with the increase of nitrogen application for 4 years. Soil nitrate nitrogen in both soil layers increased with the increase of nitrogen application. The contents of microbial biomass carbon (MBC) and MBN in both soil layers under HN treatment were the lowest after 8 years of nitrogen application. The content of ammonium nitrogen in the 0–10 cm soil decreased significantly with the increase of nitrogen application, while the content of nitrate nitrogen increased significantly. 2) HN treatment increased β-glucosidase (βG) activities in both soil layers after different years of nitrogen application, but 8 years of HN treatment significantly decreased β-N-acetylglucosaminidase (NAG) activity in the 0–10 cm soil. Four years of LN and HN treatments significantly increased the activity of acid phosphatase (ACP) in the 0–10 cm soil, but significantly decreased ACP activity in the 10–20 cm soil. 3) Under different nitrogen application years, the vector angles of soil enzyme stoichiometric ratios at different soil depths were all greater than 45°, moreover, the vector angles of soil enzyme stoichiometric ratios under nitrogen application for 8 years were significantly greater than that for 4 years, indicating that long-term nitrogen application exacerbated soil microbial Phosphorus limitation. Under different nitrogen application years, the stoichiometric ratios of soil enzyme C∶N∶P were 1∶1∶2 in the 0–10 cm and 1∶1∶3 in the 10–20 cm soil layers, which deviated from the ratio of soil enzyme activity C∶N∶P in global ecosystem (1∶1∶1). 4) Redundancy analysis (RDA) showed that DON, MBN and NH₄⁺-N were the main factors regulating the changes of soil enzyme activities and stoichiometric ratios in two soil layers for different nitrogen application years. In conclusion, long-term nitrogen deposition significantly aggravates soil phosphorus limitation in subtropical regions.