Leymus chinensis (Trin.) Tzvel. (Poaceae) is the dominant plant species in the Songnen grassland of China. Nitrogen addition is an important measure to prevent degradation of grassland due to soil salinization. To clarify the effects of long-term nitrogen addition on the quality of L. chinensis and soil properties, a field experiment was continuous conducted for 10 years in moderately saline-sodic grassland from 2009 to 2018, and the annual nitrogen addition rate was 0，30，60，90，120，150，180 and 210 kg N ha-1, respectively. The results showed that with nitrogen addition rates increasing, the contents of protein and fat in shoot increased 20.5% to 80.9% and 6.9% to 69.3% compared with those of the control without nitrogen addition, respectively. When nitrogen addition rates reached 90 kg ha-1 to 210 kg ha-1, The ratio of K+/Na+ and Ca2+/Na+ in L. chinensis shoot increased 1.26 to 3.37 times and 1.56 to 2.98 times compared with those of the control, respectively. Nitrogen addition decreased significantly soil pH, electrical conductivity and exchange sodium percentage, and increased significantly the contents of soil organic matter, total nitrogen, available nitrogen, the activities of sucrase and urease and ecosystem multifunctionality(P＜0.05). The redundancy analysis showed that there was a significant positive correlation between the improvement of L. chinensis quality and soil desalination and soil fertility increasing. Therefore, the suitable nitrogen addition rate of 90-120 kg N ha-1 was an effective and necessary measure to maintain the healthy growth of L. chinensis and inhibit land degradation in moderately saline-sodic grassland of Northern China.