Dispersive XAFS is applicable to the millisecond time-resolved sequential measurement. DXAFS apparatus consists of a bent crystal (polychromator) and a position sensitive detector. There is no mechanical movement during the measurement. The time resolution of DXAFS is suitable to analyze chemical reactions started by introducing a reactant. XAFS spectrum of short-lived reaction intermediate can be obtained from DXAFS experiment. The formation of intermediate CoO species has been confirmed during the oxidation process of supported Co catalyst to Co₃O₄. Reaction kinetics is also an important information obtained from the time change of X-ray absorbance. The reaction mechanism of H₂ reduction process of supported metal oxide catalysts was analyzed by the DXAFS technique. It is clarified that the oxygen migration process is a key step in the reduction of supported metal oxides.