La-Ce codoping nano-TiO2 catalyst was prepared by microwave-assisted sol process with TBT and distilled water as forerunner body, ethanol as solvent and glacial acetic acid as inhibitor. The prepared samples were characterized by using XRD, XPS and UV-Vis techniques. Results of structural characterization indicated that the prepared samples were all pure anatase phase nano-TiO2 and their diffraction peak broadened obviously after La and Ce doping. Results of XPS analysis revealed that La—O bond existed in the samples and many oxygen vacancies were produced on the surface of TiO2 nanoparticles after La and Ce codoping. UV-Vis absorption spectra demonstrated that the prepared samples had strong and wide absorption band between 200 and 400 nm and the absorption intensity increased after La and Ce doping because of La(Ⅲ)—O charge-transfer transition, Ce(Ⅳ) f→d transition and Ce(Ⅳ)—O charge-transfer transition. Photocatalytic experiment results showed that the titanium dioxide’s photocatalytic activity increased obviously after La and Ce codoping. The optimal parameters for the preparation were obtained by adjusting the mole ratio of La and Ce in photocatalysts. When the doping amount of La and Ce was 2% and 0.04% respectively, the prepared sample exhibited high photocatalytic activity, the decoloration ratio of methyl orange solution was above 90%, and COD removal of cigarette factory wastewater was 86.11%.