Abstract: Nitrogen, as an essential and important nutrient for plant growth and development, has been continuously increasing globally due to the rapid development of agriculture and industry, as well as the interference of human activities and fossil fuel combustion. Nitrogen deposition can effectively increase the available nitrogen in the soil to a certain extent, and can also promote the accumulation of nitrogen elements in plants. However, relevant research has shown that an appropriate amount of nitrogen can assist in the healthy growth and development of vegetation, but excessive nitrogen accumulation can inhibit plant growth and further reduce its primary productivity. In order to improve the growth efficiency of Pinus armandii seedlings, an experimental study was conducted to determine the effect of liquid nitrogen fertilizer application concentration on the growth indicators and biomass of Pinus armandii seedlings.