Abstract: To illustrate the toxic effects of Cd2+ on plants and their tolerance mechanisms, the physiological responses of Arabidopsis thaliana L. under different Cd2+ treatments (0, 20, 40, 60 and 80 μM) were investigated. The results showed that compared to control plants, there were significantly lower biomass and root length of plants in Cd2+ treatments (P<0.05). The application of Cd2+ induced obvious DNA injury in plant roots, and caused significant inhibitory effects on SOD and POD activities (P<0.05). 20 μM or higher Cd2+ concentrations can lead to high oxidative stresses on the biomacromolecules of plant. The photosynthetic pigments contents of A. thaliana were gradually decreased following increased Cd2+, and statistically significant effects were observed under 60 and 80 μM Cd2+ treatments (P<0.05), indicating that the high Cd2+ treatments inhibited photosynthesis of plants. The soluble protein and MDA contents increased obviously following increased Cd2+ concentrations, and significantly higher contents of them were observed in 60 and 80 μM Cd2+ treatments than that in the control (P<0.05), indicating that membrane lipid peroxidation were induced by high Cd2+ application. The glutathione and phytochelatin contents of plant showed significant increases following increased Cd2+ concentrations (P<0.05). There were also higher contents of flavonoid and anthocyanin in the plants under Cd2+ treatments, indicating that accumulation of secondary metabolites with antioxidant activities was one of the strategies in A. thaliana to improve their Cd2+ tolerance. The present study could provide experimental data on the exploration of the molecular mechanisms of toxic effects of Cd2+ on plants and their tolerance strategies.