Abstract: The adsorption properities of ethlene on Pd-V-Ti-Mo oxide/SiO₂ and Pd-Voxide/SiO₂, V₂O₅/SiO₂, PdO/SiO₂, SiO₂ were investigated by pulse chromatography.On both Pd-V-Ti-Mo oxide/SiO₂ and pd-Voxide/SiO₂ catalysts the irreversible adsorption and reversible adsorption of ethylene were measured respectively. The reversible adsorption in our experimental conditions does not play a direct role in oxidation reaction.No irreversible adsorption of ethylene on PdO/SiO₂, V₂O₅/SiO₂ and SiO₂ was exhibited. However, the irreversible adsorption of ethylene on Pd-V-Ti-Mo oxide/SiO₂ and Pd-Voxide/SiO₂ was very obvious. It is also shown that the amount of irreversible adsorbed ethylene on Pd-V-Ti-Mo oxide/SiO₂ catalyst containing 0.05% Pd and its correlated activity of oxidation were all the highest. So the authors consider that there is a direct relationship between irreversible adsorption and the reactivity of selective oxidation of etylene, and the active centers are, perhaps, caused by Pd-Vconbination.The active surface area was calculated and the effect of preadsorbed oxygen on chemisorption of ethylone was examined By-product (CO₂) does not make catalysts poisoned.