There is controversy over whether the addition of nitrogen (N) is the key to the rapid growth of Chinese rye grass Leymus chinensis (Trin.) Tzvel. in natural, semiarid grasslands. We investigated yearly impact of various N additions (0, 91, 183, and 274 kg N ha−1) on the relationships between nutrient traits (plant carbon [C], N, and phosphorous [P]), morphological traits (plant height, leaf number, leaf length, leaf width, stem length and stem diameter) and aboveground biomass in L. chinensis. Results showed that most of the growth characteristics of L. chinensis increased with N rate except for leaf number and stem length. Nitrogen addition increased aboveground biomass, plant height, leaf length and stem length of L. chinensis, which was related to high precipitation during the critical period for the growth of L. chinensis. Nitrogen addition increased the N concentration and N to P ratio of L. chinensis tissue, but decreased the C to N ratio in the leaf and stem of L. chinensis. Compared to the control, N addition increased C and N concentrations and the N to P ratio, but decreased P concentration and the C to N ratio.