The invention belongs to the technical field of an inorganic membrane material, and in particular relates to an ordered mesoporous TiO2-SiO2 nano-composite membrane and a preparation method thereof. The acidity of sol and the factors such as the peripheral environment temperature, the relative humidity and the organic solvent volatilization rate in the membrane forming process are regulated and controlled in a combined and synergistic mode, so that inorganic precursor molecules and oligomer thereof as well as template agent molecules are synchronously self-assembled on the surface of a carrier in the solvent volatilization process to form an ordered organic-inorganic hybridized mesostructure gel membrane; and the ordered mesoporous TiO2-SiO2 nano-composite membrane is prepred through the processes of hydrolysis, cross linking and polymerization of the inorganic precursors, drying and roasting of the gel membrane, removal of the template agent, high-temperature pore-wall crystallization and the like. The method is repeatable and controllable in synthesis condition. The prepared composite membrane mesoporous structure has high order degree and high heat stability, the membrane thickness can be controlled within a certain range, and the property of degrading algal toxin by the membrane under the conditions of room temperature and ultraviolet light irradiation and in liquid phase is remarkable.