Nitrogen (N) addition strongly influences community composition and ecosystem functioning. However, little is known about their effects on seeds yield attributes of Leymus chinensis (Trin.) Tzvel. in Songnen Plain, China. A field experiment was evaluated in Songnen Plain to investigate the effects of N addition on seeds yield and yield components of L. chinensis. The experiment consisted of five N addition levels (0, 2.9, 5.9, 9.0, 11.9 g N m 2 yr -1 ) was conducted for two consecutive growing seasons. The results showed that, except spikelet number, the other plant characteristic, such as plant height, leaf area, seed setting rate, 1000-grain weight, and seeds yield, were significantly influenced by N addition in the both growing seasons. With increasing N addition, the reproductive seed setting rate, grains number and weight can improve the seed yield in growing season and heading year. Although N addition has the more significantly effect on the seeds yield and yield components (besides spikelet number) in later fall, raised N addition in topdressing did not cause a standing increase trend. Therefore, from our results, the optimal N addition of application 5.90 g m -2 with a method of topdressing in late fall were recommended to improve the seed yield and yield components of L. chinensis in Songnen Plain, China.