Oxidized low density lipoprotein (oxLDL) is thought to be a key proatherogenic event. The oxidation of LDL induced by Cu2+ at different time was studied by UV-Vis absorption spectra and circular dichroism (CD) spectra. It was shown that long oxidation time is accompanied by an increased MDA content and fluorescence intensity at 430 nm, which suggested new product. The intensity of UV absorption peak of LDL increased, while fluorescence and synchronous fluorescence intensities, which typified amino acids, decreased. CD data displayed that α-helical content of the protein decreased and the secondary structure changed. The results indicated that during the process of oxidation of LDL Cu2+ induced not only the product but also the change of the conformation of apoB-100.