In situ ordered FePt thin films with face-centered-tetragonal (fct)-(001) texture have been prepared by magnetron sputtering the FePt layer onto the Cr100-xRux underlayer at relatively low temperature. The dependence of FePt texture on the Ru content in the Cr underlayer and the substrate temperature is investigated. Addition of Ru in Cr underlayer results in the formation of the FePt ordered phase in a lower substrate temperature (350°C) with c-axis orientation perpendicular to the film plane. Good perpendicular magnetic properties are obtained in films with Cr 91Ru9 underlayer. A thin Pt intermediate layer is introduced between the FePt layer and the CrRu underlayer, which is found to effectively resist the Cr diffusion from the CrRu underlayer into the FePt layer and results in better FePt fct-(001) texture and improved magnetic properties.