Chemical elements, such as carbon (C), nitrogen (N) and phosphorus (P), are major limiting nutrients in arid and semi-arid grasslands and their stoichiometry (C:N:P) is a very important ratio to determine. In addition, it is critical to understand how plant stoichiometry responds to multiple environmental factors at the species level. In this study, we conducted a greenhouse experiment to investigate the effects of salt stress (4 g NaCl/kg soil), drought (35% of the soil water holding capacity) and N addition (10 g N/m(2)), as well as their interactions, on C, N and P concentrations and C:N:P ratios in two dominant species (Allium polyrhizum and Stipa krylovii) from the Hulunbuir grassland of Inner Mongolia. Allium polyrhizum had higher N and P concentrations, and lower C:N and C:P ratios than Stipa krylovii. Salt stress significantly decreased plant C concentration, while drought had no significant effects on all the study variables of the two plant species. Nitrogen addition significantly increased plant N concentrations, and decreased C:N and C:P ratios. There were significant interactions between salt stress and species identity in affecting plant C and N concentrations as well as C:N and N:P ratios. This study could further enrich the knowledge of plant stoichiometry in response to multiple environmental stresses.