Increasing atmospheric nitrogen deposition is one of the hot topics related to global climate change. Studying the effects of nitrogen deposition on morphological and physiological characteristics of plants increasingly becomes a major focus in the field of ecological sciences. We conducted a field manipulation experiment to study the response of Photosynthetic characteristics and leaf functional traits of Leymus chinensis in response to simulated nitrogen deposition in a Stipa baicalensis grassland in inner Mongolia. This study was conducted during 2010-2015, five treatments including 0 kg?hm~(-2)(CK)、30 kg?hm~(-2)(N30)、50 kg?hm~(-2)(N50)、 100 kg?hm~(-2) (N100)、150 kg?hm~(-2)(N150)were conducted. Forty-eight (8 m*8 m) plots were established with 2 m belts between treatment areas, respectively. The results showed that the light saturation point (LSP) of N30, N50, N100, N150 significantly lower than that of CK by 40.32, 19.73, 38.18, 37.75 percent, respectively (P<0.05). Maximum net photosynthetic rate (P_(nmax)) of N30, N50, N100, N150 were significantly lower than that of CK by 22.51, 48.56, 27.43, 50.72 percent, respectively (P<0.05). Leaf N content (N_(mass)), leaf P content (P_(mass)) and leaf construction cost (CC_(mass)) of N30, N50, N100, N150 were significantly higher than that of CK. Photosynthetic energy use efficiency (PEUE) and photosynthetic nitrogen use efficiency (PNUE) of N30, N50, N100, N150 were significantly lower than that of CK. Correlation analysis showed that P_(nmax) were positively correlated with PEUE and PNUE (P<0.01), leaf N_(mass) were positively correlated with specific leaf area (SLA), P_(mass) and CC_(mass) (P<0.01), CC_(mass) were positively correlated with SLA (P<0.01). In summary, nitrogen deposition induced the decrease of PEUE, PNUE of Leymus chinensis, and the increased leaf mass and leaf N/P.