Macroporous TiO2 films have been prepared by sol-gel method without any surfactant and colloidal templates where the gel TiO2 films deposited from the precursor solutions containing photomonomer were irradiated by the UV light for some time. The UV irradiation could induce the monomer to polymerize, which resulted in two phases in the films, one was the emerging polymer-rich phase, and another was the residual monomer-TiO2 oligomer-rich phase. After the UV irradiation, the films were heat treated at 600 degrees C for 10 min, then a well-defined interconnected macroporous TiO2 films could be obtained. X-ray diffraction, scanning electron microscopy, atomic force microscopy, and thermogravimetric and differential thermal analysis were used to characterize the macroporous TiO2 films. The results showed that the macroporous structures of the films could be tuned by changing the reaction parameters. The highly macroporous TiO2 films prepared by the monomer polymerization exhibited much higher photocatalytic activity for the photodecomposition of methylene blue dye than that of the TiO2 films prepared without the monomer polymerization. This sol-gel method without surfactant and templates is useful in the preparation of the porous TiO2 thin films with high photocatalytic activity and the desired pore structure.