Disagreements over the effects of nitrogen deposition on soil respiration still exist, thereby necessitating further studies. In the present study, we designed an experiment to explore the seasonal responses of soil respiration to various levels of nitrogen deposition (T₀: 0 g N m^-2 a^-1as the control; T₅: 5 g N m^-2 a^-1 as the low N treatment; T₁₀: 10 g N m^-2 a^-1 as the moderate nitrogen treatment; and T₁₅: 15 g N m^-2 a^-1 as the high nitrogen treatment. All treatments were performed with nine replicates both in the Masson pine forest and in the Citrus plantation at Mt. Jinyun, Chongqing, China. The different levels of N addition were applied four times at the beginning of each season from May 2014. We measured soil respiration, soil temperature, and soil moisture simultaneously by using the Automated Soil CO₂ Exchange Station (ACE, UK) for four consecutive days in July, September, November, January, February, March, May, and June, respectively, at four times each day between 8:00 and 6:00. The results showed that:(1) the two forests underwent similar seasonal changes in soil respiration, with the most change being observed during the summer, followed by spring, autumn, and winter, which yielded the least change. However, the citrus plantation presented significantly higher levels of soil respiration than the Masson pine forest across all seasons (P < 0.05). (2) Generally, nitrogen deposition suppressed soil respiration in both forests and these inhibitory effects were strengthened with increasing levels of nitrogen deposition. The only exception in which nitrogen deposition enhanced soil respiration was in the Masson pine forest during the winter, while soil moisture was very low. (3) Soil respiration showed significantly positive exponential relationships with soil temperature (P < 0.01) and significant quadratic relationship with soil moisture (P < 0.05). Both factors (soil temperature and moisture) are influenced by the levels of nitrogen deposition in subtropical forests. Thus, the results of our study on subtropical forests confirm the theory that nitrogen deposition inhibits soil respiration.