Effects of uniconazole on the growth and activitives of anti-oxidation enzymes of Elodea nuttallii were studied. The results showed that uniconazole could stimulate the sprout bourgeoning but restrain the growth of frond remarkably. The internode length of the new branches was smaller and leaves grew closely. Low concentrations of uniconazole increased the content of chlorophyll a at the beginning of the exposure, and, at longer exposure time, chlorophyll a content decreased, but chlorophyll b content increased greatly. Anti-oxidation enzymes of Elodea nuttallii were sensitive to the exposure of uniconazole. The activities of SOD (superoxide dismutase) were greatly induced, and the activities of CAT (catalase) increased first and then decreased. The activities of POD (peroxidase) increased at the beginning, then decreased, and then increased again. The results revealed that uniconazole could result in oxidative stress to Elodea nuttallii, and induce elevated activities of anti-oxidation enzymes. When stress intensity exceeded a certain value, reactive oxygen species could not be removed in time and would result in oxidative damages to the plant.