The invention discloses a preparation method of a biferroelectric bismuth ferrite/bismuth vanadatephotoelectrochemical film. The method comprises the following steps: 1) performing FTO pretreatment; 2) dissolving bismuth nitrate pentahydrate and potassium iodide in water, and adding metal salt ions and nitric acid to adjust the pH value; 3) dissolving p-benzoquinone in ethanol; 4) mixing the two,and performing electrochemical deposition to obtain a film electrode; and 5) dropwise adding dimethyl sulfoxide in which ferrous acetylacetonate and vanadylacetylacetonate are dissolved into the filmelectrode obtained in the step 4), and carrying out high-temperature heat treatment in a tubular furnace to obtain the biferroelectric doped bismuth ferrite/bismuth vanadatefilm. According to the preparation method of the biferroelectric bismuth ferrite/bismuth vanadatephotoelectrochemical film, the preparation method is simple and easy to implement, the requirement for the size and shape of a bottom electrode is low, the film is uniform in quality, large in specific surface area, accurate in stoichiometric ratio, excellent in photocatalytic performance and high in water photolysis efficiency,and doping modification research is easy to carry out.