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Ru-modified monolayer-dispersed WO x /CeO 2 hybrid composites were prepared by co-impregnation (CI) and step impregnation (SI) methods, and the effects of active site distribution on the catalytic oxidation of 1,2-dichloroethane (DCE) were investigated. Ru species tends to be deposited on the monolayer-dispersed WO x (m-WO x) by SI method, which can increase the oxygen vacancies (O V,m-WOx) at m-WO x /CeO 2 interfaces. Abundant O V,m-WOx can promote the formation of more active W–OH and accelerate the dechloridation and oxydehydrogenation of DCE. Oppositely, for CI method, Ru species exists mainly in the form of Ru−O−Ce bonds, increasing the oxygen vacancies (O V,RuCe) into CeO 2 surface lattices and promoting the deep oxidation of intermediate products. The closer contact between the two hetero-interfacial oxygen vacancies (O V,RuCe and O V,m-WOx) on Ru-modified m-WO x /CeO 2 produces a stronger synergistic effect on DCE activation and oxidation, and meanwhile advantageously inhibits the adsorption of chlorine species as well as the formation of polychlorinated by-products. [Display omitted] • Impregnation sequence affects active site distribution on Ru-modified m-WO x /CeO 2 catalysts. • Ru species on m-WO x surfaces increases O V,m-WOx and W–OH by SI method. • CI method generates more Ru−O−Ce and O V,RuCe. • Synergies of hetero-interfacial O V promote DCE activation/oxidation and inhibit Cl species absorption. [ABSTRACT FROM AUTHOR]