Cu-loaded MgAl hydrotalcite catalysts were synthesized by impregnation method and further used for catalytic wet peroxidation (CWPO) of methyl orange (MO) using hydrogen peroxide as oxidant. The synthesized catalysts have been characterized by XRD, SEM/EDS, TG/DTA, XPS, H-2-TPR and BET. The characterizations showed that a good dispersion of Cu species inside the MgAl hydrotalcite supports, where Cu2+ and Cu+ species were coexistence, mainly existed as Cu2+ <-> Cu+ pairs. The CuMgAlO catalyst showed the highest catalytic activity due to the high content of Cu2+ <-> Cu+ pairs, stable performance during reuse for five cycles with fewer copper leaching. The degradation mechanism of MO was determined by UV-vis, ATR-FTIR and GC-MS. The hydroxyl radicals (HO center dot) induced strong oxidizing effect, where the azo groups (-N=N-) double bonds would be first attacked by the hydroxyl radical and other free radicals. With the continuous oxidization, these intermediates could be oxidized to the final oxidation products, such as water and carbon dioxide. (C) 2016 Elsevier B.V. All rights reserved.