The invention discloses a preparation method of a rare earth composite boron-nitrogen co-doped titanium dioxide catalyst, relates to a preparation method of a photocatalyst material, and belongs to the technical field of titanium dioxide photocatalyst. The invention aims to solve the problems that in the prior art, the cost is high, the energy consumption is huge, and the pollution is serious. The preparation method comprises the following steps: step one, preparing a rare earth salt solution; step two, preparing TiO2 suspension; step three, dispersing and drying through baking; step four, burning. The preparation method has the advantages of simple technology, convenient operation, low cost, little energy consumption, and no pollution. The prepared rare earth composite boron-nitrogen co-doped titanium dioxide catalyst has a good adsorption performance in visible light catalyzed reactions and high photocatalytic activity. The provided preparation method is used to prepare a rare earth composite boron-nitrogen co-doped titanium dioxide catalyst.