Abstract: The mesoporous Ce1-xLaxO2 (x=0-0.3)composite oxide materials were synthesized via a facile approach of evaporation-induced self-assembly (EISA) in the presence of acetate salt as inorganic species and triblock copolymers P123 as surfactant. The X-ray diffraction, transmission electron microscopy and N2 adsorption-desorption testing were employed to characterize the morphology, structure and catalytic performance of the mesoporous Ce1-xLaxO2 composite materials. The results show that the structure of the products Ce1-xLaxO2 were solid solutions with a single cubic phase when x=0.1 and x=0.2. However, when x=0.3, the product was a compound of Ce1-xLaxO2 solid solution and La2O3. The catalytic activity of Ce1-xLaxO2 was enhanced with the increase of the lanthanum content. Moreover, the ability of Ce0.7La0.3O2 had good decolorization ability on methylene blue solution , and the decolorizing rate almost reached 100% after reaction for 30 min.