We synthesized $TiO_2$ ($Ru_x/TiO_2$) incorporating $TiO_2$ and Ru via an one-step hydrothermal method. The physical properties were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The prepared samples were applied as a catalyst for the oxidation of benzyl alcohol to benzaldehyde using molecular oxygen ($O_2$). Especially, the catalytic activities increased as the contents of ruthenium in $TiO_2$ increased without the formation of any byproducts.