Promotional effect of Ca on the catalytic property of Pd/Ce-Zr/Al2O3 catalyst towards methane combustion is examined. The surface properties and the oxidation/reduction behavior of these catalysts are investigated by BET, TEM, XPS, TPR, TPO and TPSR techniques. Activity tests in methane combustion show that addition of Ca to Pd/Ce-Zr/Al2O3 can promote remarkably its low-temperature activity. The thermal stability of the Pd/Ce-Zr/Al2O3 catalyst to the exposure at high temperature is also enhanced by Ca loading. XPS and TEM results show that the addition of Ca to Pd/Ce-Zr/Al2O3 catalyst generates well-dispersed PdO particles on support. H-2-TPR, O-2-TPO and CH4/O-2-TPSR experiments show that the addition of Ca improves the reduction/reoxidation properties and thermal stability of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce-Zr/Al2O3 catalyst. (C) 2008 Elsevier B.V. All rights reserved.