The cerium oxide films with high refractive index and good UV irradiation shielding performance were synthesized on the glass substrates by a hydrothermal method using Ce(NO3)3·6H2O and CO(NH2)2 as raw materials. The films and the powders prepared at the same time were characterized by SEM, XRD, FT-IR, ellipsometer and UV-vis. The influences of original Ce(Ⅲ) concentration and urea dosage on cerium oxide films were researched. The results show that the films are smooth and the particles are small at low Ce(Ⅲ) concentration and urea dose. The sediments are cerium oxide and Ce(CO3)2O·H2O crystal, and silicon of substrate is involved in hydrothermal reaction. Meanwhile, the film refractive indexes are affected by film compact and chemical composition. Both of absorbance and absorption wavelength edge become big with increasing of Ce(Ⅲ) concentration and urea dose, and the main influence factors are the film thickness and composite semiconductors. The optimal Ce(Ⅲ) concentration is 0.008 mol/L, and the optimal urea dosage is 0.06 g.