Abstract: Abstract: Cucumbers were used to study the effect of seed germination and the activity of hypocotyls superoxide dismutase(SOD), peroxidase (POD), catalase (CAT) and the content of malondialdehyde (MDA) responsing to different concentrations of nickel (Ni2 +) stress. The results indicated that: Ni2 + treatment has activative effect under low concentrations but inhibitory effect under high concentration for cucumber seed germination, and the inhibitory effect gradually increases with the increasing concentration; the content of MDA in cells increases slightly at low concentrations of Ni2 +, and then increases gradually as the concentration of nickel increases ; the activity of SOD and CAT in the endogenous protective enzyme system increases first and then reduced with the increasing concentration of Ni2 +.However,the activity of POD keeps increasing with the increasing concentration of Ni2 +.