The nitrogen (N) content of plant functional groups (PFGs) is vital to understand the nitrogen-induced biodiversity loss under the context of enhanced N deposition globally, and it is also an important parameter in process models that simulated productivity, e.g., net primary productivity and gross primary productivity in Biome-BGC model. Considering the strong impacts of nitrogen availability and the regulation of phosphorus (P) limitation, we conducted a four-year manipulative experiment to clarify the responses of N content of PFGs to N and P additions (N addition: 10 and 40 g N m^-2 a^-1, P addition: 5 and 10 g P m^-2 a^-1) in a temperate steppe of the Inner Mongolia, China. Our results showed that: (1) N addition significantly increased the N content of the community and three PFGs. Grasses (10 g N m^-2 a^-1) and shrubs (10 and 40 g N m^-2 a^-1) had significantly larger increase of N content than that of forbs with the same rate of N addition. There was no significant difference among different rates of N additions for the same PFG or the whole community. (2) Nomatter what rates of P additions, i.e. 5 or 10 g P m^-2 a^-1, there was no significant effects of P addition on N content of the community or the three PFGs. However, the P-induced changes of shrubs (5 and 10 g P m^-2 a^-1) and grasses (10 g P m^-2 a^-1) were significantly higher than that of grasses (10 g P m^-2 a^-1). (3) Compared to N addition, the simultaneous additions of N and P significantly increased the N content of communities, grasses, and forbs but not shrubs, and the increase tended to be larger with the increasing rates of N or P additions. (4) Compared to N addition or the control, the simultaneous additions of N and P significantly increased the P content but decreased the N/P ratios of the communities and the three PFGs. The largest increase in P content was observed in grasses and forbs at the same rate of P addition. Notably, the P-induced increase of P content in grasses was inclined to be greater in the treatments with higher rates of P addition, and it was also the grasses got a lower N/P ratio in the treatments with higher rates of N and P additions. Our findings have important implications for grassland management and provide a better understanding of how grassland ecosystems respond to global changes.