Abstract: The physiological and biochemical indexes of Alternanthera philoxeroides were investigated with different contents of Zn in Hoagland cultivation. When the pollution caused by Zn at the low concentration of Zn (10mg•L-1)，the plant external injury of Alternanthera philoxeroides was not significant. At the concentrations of Zn (＜50mg•L-1)，the protection enzyme in cells such as SOD，POD and CAT increased. But with the Zn level increasing, the plants grew slowly, the biomass decreased, and the chlorophylls level decreased. Meanwhile the balance of these kinds of enzymes was destroyed in the active oxygen scavenging system。The accumulation of O2•- and H2O2 cannot be prevented effectively, the cell membrane permeability increased, the MDA content accumulated highly. Thus the growth of plant was affected, and toxic symptoms appeared.