Mounting evidence has shown that dyshomeostasis of the redox-active biometals such as Cu and Fe can lead to oxidative stress, which plays a key role in the neuropathology of Alzheimer’s disease (AD). Here we demonstrate that with the formation of Cu(Ⅱ)-Aβ1-40 complexes, copper markedly potentiates the neurotoxicity exhibited by β-amyloid peptide (Aβ). A greater amount of hydrogen peroxide was released when Cu(Ⅱ).Aβ1-40 complexes was added to the xanthine oxidase/xanthine system detected by potassium iodide spectrophotometry. Copper bound to Aβ1-40 was observed by electron paramagnetic resonance (EPR) spectroscopy. Circular dichroism (CD) studies indicated that copper chelation could cause a structural transition of Aβ. The addition of copper to Aβ introduced an increase on β-sheet as well as α-helix, which may be responsible for the aggregation of Aβ. We hypothesized that Aβ aggregation induced by copper may be responsible for local injury in AD. The interaction between Cu2+ and Aβ also provides a possible mechanism for the enrichment of metal ions in amyloid plaques in the AD brain.