The invention relates to zinc oxide/cuprous oxide nano heterojunction photocatalytic material, wherein the zinc oxide has the molecular formula of ZnO, and the cuprous oxide has the molecular formula of Cu2O. The ZnO/Cu2O nano heterojunction photocatalytic material comprises a silicon substrate, a Cu2O film and ZnO nano rods, wherein the Cu2O film is deposited on the silicon substrate, and the ZnO nano rod grows on the liquid phase of the Cu2O film. The method for preparing the ZnO/Cu2O nano heterojunction photocatalytic material comprises the following five steps: (1) preparing a substrate; (2) vacuumizing a sputtering film forming cavity; setting all parameters of a magnetically controlled sputtering device and depositing a Cu2O thin film layer; (4) obtaining a Cu2O thin film after stopping the magnetically controlled sputtering device for 30min; and (5) vertically putting the silicon substrate on which the Cu2O thin film is deposited into a beaker containing the mixed solution of zinc acetate and hexamethyleneimine, putting the beaker in a water-bath kettle to preserve heat for 6 hours, taking the beaker out of the water-bath kettle, cooling the beaker to room temperature, cleaning the beaker with deionized water, and drying the beaker at room temperature to obtain the growing ZnO nano rod array. The invention has wide use value and application prospect in the field of the preparation technology of the nano heterojunction photocatalytic material.