The invention belongs to the technical field of a photoelectric functional material, and particularly relates to an oxide-doped nanometer structure cuprous oxide photoelectric conversion thin film aswell as a preparation method and application thereof. A cuprous oxide nanometer line thin film is used as a main body; hydroxyl iron oxide nanometer particles are coated on the surface; under the thermal annealing, through interface reaction, the oxide doping nanometer structure cuprous oxide thin film is obtained. The thin film is used as a photoelectric conversion thin film of a solar battery; the photoelectric conversion efficiency can be greatly improved; the performance of the cuprous oxide solar battery is improved.