Uniform CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via the sol-gel method. The samples were characterized using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The surface state analysis by means of X-ray photoelectron spectroscopy (XPS) shows that the Ti element mainly exists as a chemical state of Ti4+, while the Ce element exists as a mixture of Ce3+ and Ce4+ oxidation states. The photocatalytic degradation of methyl orange (MeO) in CeO2/TiO2 suspension was investigated. The results indicate that the CeO2/TiO2 nanocomposites show higher photocatalytic activity than pure TiO2. Photodegradation of MeO can be improved by increasing the Ce/Ti molar ratio in the initial 15 min.