Abstract: The toxic effects of various concentrations of Cu²⁺(0,0.002,0.004,0.006,0.008 mmol·L^-1) were studied on chlorophyll content,chlorophyll fluorescence parameters,lipid peroxidation,antioxidant system and ultrastructure changes in leafs of Trapa bispinosa Roxb.The results showed that with the rise of Cu²⁺ concentration in culture medium,(1)the chlorophyll contents and chlorophyll fluorescence parameters(Fv/Fo,Fv/Fm) decreased significantly,while Fo increased gradually.(2)generating rate of active oxygen(AOS),malondialdehyde(MDA) content and the activities of peroxidase(POD),catalase(CAT) as well as ascorbate peroxidase(APX) all increased gradually.Superoxide dismutase(SOD) activity,free proline(Pro) and soluble sugar contents increased markedly.While the contents of ascorbic acid(ASA),glutathione(GSH) and glutathione reductase(GR) activity enhanced progressively and followed by a decline at the higher doses.(3)Transmission electron microscopy observation indicates that the higher Cu²⁺ concentration,the more serious damages to the leaf cells,especially chloroplast,mitochondria and nucleus.Thus,the detriment effect of Cu²⁺ of Trapa bispinosa Roxb.was resulted from disorder of physiological,biochemical metabolism and disorder of physiological metabolism.