Abstract: Pd / Al2 O3 monolithic catalysts were prepared using Al2 O3 porous material with both mesopores and three-di- mensional interconnected macropores as the support and Ce,Zr as additives. Ultra-low concentration ventilation air methane combustion activity on the as-synthesized catalysts was investigated and the reaction path was predicted. Re- sults show that the reaction performance of catalysts with the additives is excellent owing to the maintained special mi- crostructure of the original support and large BET surface value. Pd / Al2 O3 catalysts with additive Zr have a better re- action activity than addition of Ce. The possible reaction path of CH4 catalytic combustion on Pd / Zr / Al2 O3 catalyst was predicted as follows:one of the C—H bonding strength in the molecule CH4 adsorbed on the PdO-Pd active sites are decreased with the help of additive Zr to be lower than that of bonding strength between H and atom O in the PdO sur- face lattice,resulting in the escape of one atom H from the molecule CH4 and the accomplishment of the controlling step. CO2 and H2 O are generated quickly after that process.