The high-temperature oxidation/reduction cycle of Pd/PdO was investigated by high-temperature X-ray diffraction and thermogravimetric technique. Moreover, effects of minor Mn addition on the thermal stability of Pd/PdO were also studied. The results show that PdO will decompose to metal Pd sharply at a certain temperature, and the decomposition temperature is independent of powder granularity. The dispersion state of Pd powder decides the hysteresis characteristics of the phase transition Pd/PdO. Proper Mn addition can change the high temperature thermal stability and hysteresis curve of Pd/PdO system