Quantifying the content of elements in the aboveground and underground parts of plants is significant to understand and predict how plant nutrient balance responds to changes in atmosphere nitrogen deposition. A field experiment with ectomycorrhizal fungi and nitrogen was established to investigate effects on nutrient elements in Pinus massoniana seedlings under the background of increased nitrogen deposition. Seedlings were subject to nitrogen additions, which were 0 kg N hm^-2a^-1 (N0), normal nitrogen deposition 30 kg N hm^-2a^-1 (N30), moderate nitrogen deposition 60 kg N hm^-2a^-1 (N60), severe nitrogen deposition 90 kg N hm^-2a^-1 (N90), and symbiosis with ectomycorrhizal fungi (EMF), which was Pisolithus tinctorius and Suillus grevillei, a total of 12 treatments. The contents of macronutrients and micronutrients in the leaves and roots of plants were determined. It was found that nitrogen addition changed the content of nutrient elements in the aboveground and underground parts of Pinus.massoniana, and P, Ca, Fe and Mn of seedlings reached the critical value at N60. When the input amount exceeded the nitrogen requirement of seedlings, nitrogen deposition would reduce the content of nutrient elements in Pinus massoniana compared with the optimum concentration. With the increase of nitrogen application concentration, the C content in leaves of Pinus massoniana seedlings increased at first and then decreased, and reached the maximum at N60, while the nitrogen content in aboveground and underground parts increased with the increase of nitrogen application concentration. The contents of K, Ca and Mg in roots and leaves decreased with the increase of nitrogen application concentration, and nitrogen application also decreased the contents of C and micronutrients in roots. Nitrogen application also decreased the content of root C and micronutrients. However, under the same nitrogen addition, EMF could increase the content of most elements. Compared with the control, the leaf N content of N90 inoculated with Sg and Pt increased by 112.6% and 138.6%, respectively, and the root N content increased by 73.1% and 71.6%, respectively. Compared with the control without nitrogen application, the leaf P content of the plants inoculated with Sg and Pt increased by 166.3% and 132.9%, respectively, and the root P content increased by 40.8% and 38.5%, respectively. EMF can maintain the balance of plant nutrients, thus reducing the effect of high nitrogen application on plants. It provides a theoretical basis for inoculating EMF under the increase of nitrogen deposition in the future climate change scenarios to regulate the element content of plants, so as to achieve more environmental element balance to promote growth.