Controlled by weighing the soil and pots, one-year-old Koelreuteria elegans seedlings were potted under four levels of drought stress including optimal water content (CK), mild drought stress (LD), moderate drought stress ( MD) and severe drought stress ( SD) to study the growth and physiological and biochemical characteristics under drought stress. The mechanism of drought-tolerance in K. elegans was discussed. The results showed that the height and biomass of the seedlings decreased significantly but the root/ shoot biomass ratio increased obviously, and the contents of MDA, soluble sugar and proline added up; the contents of K⁺ and Ca²⁺ had a slight increase in the treatment of LD and then slowly decreased, while the content of Mg²⁺ in leaves had no obvious difference at four levels of drought stress, while the content of protein and activity of CAT, POD, SOD and APX, which were the biggest at the level of MD, increased firstly and then decreased with drought stress becoming more severe. The above results indicated that the drought stress leads to more serious peroxidation of membrane of K. elegans, which inhibited its growth. However, K. elegans could protect its membrane structure and keep normal physiological activities through improving the activity of antioxidant enzymes system and accumulating osmotic regulators such as soluble sugar, proline and soluble protein, which leads to the good performance of K. elegans to tolerate drought.