【Objectives】The objective of the study was to evaluate effects of doubled CO_2 concentration and drought stress on photosynthesis characteristics and non-structural carbohydrates (NSC) of Bothriochloa ischaemum, and provide scientific basis for the growth of B. ischaemum under future elevated CO_2 concentration in arid and semi-arid areas. 【Methods】 Using the split plot design, the effects of doubled CO_2 concentration and drought stress on the photosynthesis and NSC contents in B. ischaemum were investigated. The main plot was two CO_2 concentrations (ambient CO_2 concentration, 400 mumol/mol, and doubled CO_2 concentration, 800 mumol/mol), and the split-plot was three water treatments (severe drought stress, 35%-40% field capacity (FC), moderate drought stress, 55%-60% FC, and control, 75%-80% FC). 【Results】 The results showed that the parameters of photosynthesis-light response curves of B. ischaemum and the NSC contents were significantly influenced by the doubled atmospheric CO_2 concentration and drought stress, while there were no significant synergetic effects between them. The doubled CO_2 concentration significantly increased the maximum photosynthetic rate (P_(max)), apparent quantum yield (AQY), light saturation point (LSP) and light compensation point (LCP) (P < 0.01), while the drought stress significantly decreased P_(max), AQY and LSP (P < 0.01). The doubled CO_2 concentration and drought stress increased the soluble sugar content in the aboveground part of B. ischaemum. Under ambient CO_2 concentration, the moderate drought stress and severe drought stress significantly decreased the starch contents in the aboveground and root parts of B. ischaemum. The doubled CO_2 concentration increased the starch contents in the aboveground part of B. ischaemum by 17.4%, 44.2%, and 18.7%, respectively under the control, moderate drought stress and severe drought stress, and in the root part by 17.3%, 88.4%, and 54.4%, respectively. Under ambient CO_2 concentration, the moderate drought stress and severe drought stress significantly decreased the NSC contents in the root part of B. ischaemum. Under the doubled CO_2 concentration, the NSC contents in the aboveground part were significantly increased under the control and moderate drought stress treatments, and the NSC contents in the root part were significantly increased under the moderate drought stress and severe drought stress treatments. Under ambient CO_2 concentration, the moderate drought stress and severe drought stress significantly increased the ratios of soluble sugar contents and NSC contents in the aboveground and root parts of B. ischaemum. Under the doubled CO_2 concentration, the severe drought stress significantly increased the ratio of soluble sugar content and NSC content in the aboveground part of B. ischaemum, and the ratios under the control and moderate drought stress had no significant difference. 【Conclusions】Drought stress facilitated the transfer of starch into soluble sugar, and increased the soluble sugar content and decreased the starch content. The doubled CO_2 concentration increased the starch contents and NSC contents in the aboveground part and root part, and provided the source of soluble sugar that maintained metabolic activities and survival during the drought event. Therefore, it is speculated that in arid and semi-arid areas, elevated CO_2 concentration could increase plant photosynthesis, increase NSC accumulation, alleviate the adverse effect induced by drought stress, and improve the drought resistance. Our findings provided new insights into the underlying mechanisms and responses of plant species to future climate changes.