Understanding the structures and reaction mechanisms of interfacial active sites in the Fisher-Tropsch synthesis reaction is highly desirable but challenging. Herein, we show that the ZrO₂-Ru interface could be engineered by loading the ZrO₂ promoter onto silica-supported Ru nanoparticles (ZrRu/SiO₂), achieving 7.6 times higher intrinsic activity and ~45% reduction in the apparent activation energy compared with the unpromoted Ru/SiO₂ catalyst. Various characterizations and theoretical calculations reveal that the highly dispersed ZrO₂ promoter strongly binds the Ru nanoparticles to form the Zr-O-Ru interfacial structure, which strengthens the hydrogen spillover effect and serves as a reservoir for active H species by forming Zr-OH* species. In particular, the formation of the Zr-O-Ru interface and presence of the hydroxyl species alter the H-assisted CO dissociation route from the formyl (HCO*) pathway to the hydroxy-methylidyne (COH*) pathway, significantly lowering the energy barrier of rate-limiting CO dissociation step and greatly increasing the reactivity. This investigation deepens our understanding of the metal-promoter interaction, and provides an effective strategy to design efficient industrial Fisher-Tropsch synthesis catalysts.