A mechanism of how the Palladium-composite Perovskite catalyst for automotive emissions control keeps its activity long-lived is investigated by using XAFS and DANES (Diffraction Anomalous Near Edge Structure), a family of an anomalous X-ray diffraction techniques. The conventional catalysts are finely divided precious metal particles dispersed on a solid support. Since they suffers from heat in the car, their activity deteriorates because of the growth and agglomeration of the particles. Recently, however, the Palladium-composite Perovskite has been found to have retention of high catalyst activity during long-term use and ageing. In order to investigate the mechanism of such an ideal property in the atomic revel, X-ray diffraction and absorption techniques were employed. We find that as the catalyst is cycled between oxidative and reductive atmospheres typically encountered in exhaust gas, palladium reversibly moves into and out of the perovskite lattice. This movement appears to suppress the growth of metallic palladium particles.