FePt–X (X=C, TiO2, Ta2O5) nanocomposite films were deposited on MgO/CrRu/glass substrates at 350 °C by magnetron cosputtering. The comparison investigations on the magnetic properties and microstructure of FePt–X films with various dopants were conducted. All FePt–X films showed (001) preferred orientation and oxide dopants promoted the formation of magnetically soft fcc FePt phase. With 15 vol % C doping, FePt–C film with columnar grains of 7.5 nm was obtained and the out-of-plane coercivity measured at room temperature was as high as 14.4 kOe. The increase in carbon volume fraction to 20% caused the formation of two-layer structure, whereas for the 20 vol % TiO2 and Ta2O5 doping, the columnar structure of the FePt films remained and the corresponding grain sizes were 5 and 10 nm, respectively. Ta2O5 doping showed better grain isolation than the others. The out-of-plane coercivities of FePt–TiO2 and FePt–Ta2O- 5 films were 7.5 and 8.8 kOe, respectively.