Anthropogenic activities such as fossil fuel emissions and ammonium from production and application of fertilizers have elevated atmospheric nitrogen (N) deposition by three- to five-fold over the past century. Nitrogen deposition also has been accounted as one major component of global change and is predicted to increase in the future. Nitrogen additions in the atmosphere and soil have been demonstrated to alter regional and global environments and affect forest ecosystem carbon cycle, which is projected to alter the trajectory of future climate change through climate-carbon cycle feedback. Concern about the ecological effects of elevated nitrogen deposition on terrestrial ecosystems is currently increasing. The stem surface carbon flux is one major component of tree autotrophic respiration, and may represent tree growth activities and metabolism. Despite the importance of stem respiration, few studies have been conducted to examine the effects of simulated nitrogen deposition on stem respiration in forest ecosystem. In this study, response of simulated nitrogen deposition on stem respiration in a 40-year-old Larix gmelinii plantation in Northeastern China was studied. The objective was to test the hypothesis that N addition would increase stem respiration in N limited temperate forests. Nitrogen deposition experiments were initiated in April 2011. Four nitrogen deposition treatments (in three replicates) were established: Control (without N added), Low-N (5 g N m^-2 a^-1), Medium-N (10 g N m^-2 a^-1), High-N (15 g N m^-2 a^-1). Twelve plots, each with 10 m×20 m dimensions were set up, surrounded by an approximately 15 m wide buffer strip. All plots and treatments were installed randomly. Ammonium nitrate solution was sprayed monthly as 6 equal applications from May 2011 to October 2011, and May 2012 to October 2012. During each application, fertilizer was weighed, mixed with 50 L of water, and applied to each plot below the canopy using a backpack sprayer. Two passes were made across each plot in order to ensure an even distribution of fertilizer. The Control plot received 50 L water without N. A polyvinyl chloride collar (10.2 cm inside diameter×5 cm height) was cut and polished to fit the stem shape of each sampled tree,and set up on the northward side with silicon adhesive at breast height. During the growing season between April 2012 and October 2012, stem respiration was measured once a week from 10:00 to 12:00 with a Li-6400 portable CO₂ infrared gas analyzer equipped with a Li-6400-09 chamber. Stem temperature at 1 cm depth beneath the bark was simultaneously measured with a digital thermometer. The measured stem respiration was calibrated with the polyvinyl chloride collar volume and stem surface area of each sampled tree. Our results showed that stem respiration exhibited a strong seasonal pattern, with the highest rates found in July and the lowest rates in October. The estimated stem respiration during the measuring period varied from 1.33 to 4.71 μmol m^-2 s^-1 in the Control treatment, 1.60 to 5.01 μmol m^-2 s^-1 in the Low-N treatment, 1.85 to 5.38 μmol m^-2 s^-1 in the Medium-N and 1.73 to 5.96 μmol m^-2 s^-1 in the High-N treatment, respectively. Stem respiration rates showed a significant positive exponential relationship with stem temperature within all treatments. We fitted site-based models and used continuous measurements of stem temperature to estimate cumulative stem respiration for the growing season of 2012. Cumulative stem respiration in the growing season was estimated to 67.3 g C/m², 72.5 g C/m², 78.9 g C/m² and 86.5 g C/m² in the Control, Low-N, Medium-N and High-N treatment, respectively. The measured apparent temperature sensitivity of stem respiration (Q₁₀) was the lowest in the Control stand, and increased from the Control treatment to High-N treatment. The Q₁₀ for Larix gmelinii in the Control, Low-N, Medium-N and High-N treatment during the measuring period was 1.67, 1.80, 2.01 and 2.54, respectively. Stem nitrogen concentration also increased from Control treatment to High-N treatment, and peaked at High-N treatment. The estimated for stem nitrogen concentration Larix gmelinii in the Control, Low-N, Medium-N and High-N treatment during the measuring period was 1.00,1.32,2.02 and 2.35 g/kg, respectively. However, stem respiration was weakly correlated with stem nitrogen concentration. Stem nitrogen concentration explained 38.3% of variations during the measuring period of 2012. Our results suggest that simulated nitrogen deposition increased stem respiration in Larix gmelinii plantation in Northeastern China, but it may vary depending on the rate of nitrogen deposition.