The activating process of O-2 on all-metal aromatic complex surface is investigated for the first time by studying the absorption processes of O-2 to the surface of Al4Ca and studying the electron configuration of the most stable six Al4CaO2 isomers. It was found that Al-4 plane have a special ability to change the electron configuration of O-2. As a result, the O-2 absorbed on the surface of Al4Ca shows similar character to that of the active oxygen ion O-1(2)2-, which may give a base for the future research on the potential catalysis of all-metal aromatic system. (c) 2006 Elsevier B.V. All rights reserved.