Abstract: Effects of exogenous nitric oxide (NO) on antioxidant enzymes responses of root tips in the mungbean seedlings cultivated in solution under cadmium stress was explored. It wad observed that sodium nitroprusside (SNP), a NO donor, at 0.01 mmol/L and 0.1 mmol/L markedly promoted epicotyl elongation, but SNP at 1 mmol/L inhibited the seedlings growth . A decreased activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD)，and an enhanced activities of lipoxygenase (LOX), guaiacol peroxidase(POD), glutathione reductase (GR) and glutathione S-transferase (GST) occurred under cadmium treatment. Previous treament with 0.1 mmol/L SNP in solution significantly alleviated the inhibitory effect of metal on root elongation induced by cadmium, depressed lipid peroxideation as indicated by MDA contents, and increased the activities of ascorbate peroxidase and superoxide dismutase. NO did not produced any remarkable effect on the activities of glutathione S-transferase and glutathione reductase, however, NO attenutated slightly the activity of LOX and POD.