Gold-on-SrTiO3 catalysts were prepared by deposition precipitation. These Au/SrTiO3 catalysts exhibited activity for low-temperature CO oxidation. Their catalytic activity indicated that the active sites for CO oxidation were located on the perimeter interface of Au particles because the reaction rate was proportional to the total length of the perimeter interfaces of all the Au particles on the SrTiO3 supports. The interface structure between the Au nanoparticles and SrTiO3 supports was observed by aberration-corrected scanning transmission electron microscopy (STEM). The preferential orientation relationship observed between Au and the SrTiO3 crystals was (001)[010]Au//(001)[010]SrTiO3. The interface structure between Au(001) and SrTiO3(001) was revealed by STEM at the atomic scale and a model structure was proposed for the interface. [GRAPHICS] .