In this study, an experiment was carried out to study the process of stress adaptation in Lemna gibba grown under nickel stress (0-20 mg Ni L-1). The results showed that Ni concentrations in plants increased with increasing Ni supply levels and reached a maximum of 142.82 mg.kg1 DW at 0.5 mg.L-1 Ni treatments. The level of photosynthetic pigments (Chl a, Chl b, and total Chl) and soluble proteins increased upon exposure to high Ni concentrations. At the same time, the level of malondialdehyde (MDA) increased with increasing Ni concentration. These results suggested an alleviation of stress that was presumably the results of antioxidants such as superoxide dismutase (SOD), catalase (CAT) which generally increased linearly with increasing Ni levels. In addition, the proline content in L. gibba increased with increasing nickel levels.Our present work concluded that Lemna gibba has a high level of nickel tolerance and accumulation. We also found that moderate nickel treatment (0.05-5 mg.L-1) alleviated oxidative stress in plants, while the addition of higher amounts of nickel (10-20 mg.L-1) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system. Therefore, L. gibba may be used as a phytoremediator in moderately polluted aquatic ecosystems.