Participation of bulk oxide ion into the catalytic oxidation over metal oxide catalyst is summarized and its concept is discussed in this review. Rapid migration of oxide ion is realized through diffusion depending on the defect structure of metal oxide catalyst. The bulk of oxide catalyst plays an important role in the catalytic oxidation as the bank of active oxygen species and the bank function of the bulk of metal oxide catalyst with the rapid migration of oxide ion enhances both catalytic activity and catalyst life. Two typical examples to design excellent practical oxidation catalyst are introduced for the selective oxidation of olefin and effective automobile catalyst. (C) 2003 Elsevier Science B.V. All rights reserved.