Abstract: Growth, chlorophyll content, chlorophyll fluorescence parameters and activity of antioxidant enzymes in corn seedlings were investigated under hydroponics supplied with different concentrations of Cu. Root growth of corn seedlings was significantly inhibited and dry weight was decreased with 5-20 μmol.L-1 Cu. Chlorophyll content and Fv/Fm, ETR, qP and qy in leaves were also significantly decreased under excess Cu. The Cu concentrations in shoots and roots increased with increasing Cu concentration in the nutrient solution. However, most absorbed Cu by corn seedling was located in roots. At all levels of Cu treatment, the amount of Cu was substantially higher in roots than in shoots. During the 10-day Cu treatment, the activities of SOD, POD, CAT and GR initially increased and then decreased in roots. But for the leaves, short-term treatment with excess Cu had no significant effect on these enzyme activities. Prolonged exposure for 4 days resulted in increased enzyme activities. Thus, antioxidant enzymes have functions to alleviate the toxic effects of oxidative stress caused by excess Cu.