Abstract: Effects of duration of UV-C radiation on photosynthetic characteristics and activity of antioxidant enzyme in pea seedlings were studied.Results show that Enhanced UV-C radiation significantly decreased photosynthesis rate（P_n）,stomatal conductance（G_s）,intercellular CO₂ concentration（C_i）,transpiration rate(E_tr)and carboxylation efficiency（CE）.Prolonged duration of UV-C radiation increased the activities of POD and CAT,which soon declined,and kept the activity of SOD,and the content of chlorophyll gradually going down,but the content of MDA going up.The results suggest that enhanced UV-C radiation decreased activities of the antioxidant enzymes and made membrane peroxidated,thus leading to weakened photosynthesis.