Not only land use change, overgrazing and global warming, but also ozone increase induced by industrial development and automobile spread should be considered to conserve semi-arid grasslands of Northeast China. Model simulations showed that grasslands close to Beijing have suffered severe ozone exposures (ca. 50ppb). Plants growing there usually have high viability against water deficiency with closing stomata, which is to imagine the high resistance against air pollution. Then, we exposed ca. 50ppb ozone (20-100ppb) for 4 weeks in the environment-controlled growth cabinets (25°C, 55% RH in 14-h light period; 20°C, 75% RH in 10-h dark period) to evaluate the ozone impacts. Different species responded differently to ozone. Typical visible foliar injuries appeared in some, and growth reductions were induced in many species. Decrease in NAR, increase in LAR and SLA and lowering in root/shoot ratio were caused in some ozone-exposed plants. More quantitative studies on the long-term combined impacts of ozone and water stresses are necessary for conserving these semi-arid grasslands.