The method discloses a preparation method of a core-shell structure rare earth titanate-titanium dioxide composite nanometer fiber photocatalytic material. The preparation method comprises (1) dissolving polyvinyl acetate in anhydrous ethanol, adding a glacial acetic acid solution of tetrabutyl titanate into the solution drop by drop, carrying out stirring for 6h, standing the mixed solution for 3h to obtain a core titanium dioxide precursor solution, dissolving polyvinylpyrrolidone in N, N-dimethylformamide, adding aqueous solutions of an inorganic acid salt of titanium and rare earth nitrate into the solution, carrying out seal magnetic stirring at the room temperature for 6h, and standing the mixture for 3h to obtain a shell rare earth titanate precursor solution, (2) respectively adding the obtained two precursor solutions into a core injector and a shell injector, carrying out coaxial electrostatic spinning and collecting a spinning fiber membrane, and (3) calcinating the spinning fiber membrane through a program temperature-control calcination technology to obtain the core-shell structure rare earth titanate-titanium dioxide composite nanometer fiber. The preparation method is simple and can produce the photocatalytic material with a controllable structure and good performances.