The invention discloses a method for directly preparing a multi-element rare-earth-layer-shaped hydroxide thin film. A(NO<3>)<3>. 6H2O (A is one of La, Gd and Y) and Ln(NO<3>)<3>. H2O are dissolved indeionized water to prepare a rare earth ion solution with the rare earth ion concentration being 0.005-1 mol/L, then an additive is added, and after even mixing, an electrodeposition solution is obtained and put in a water bath to reach the required temperature; and a three-electrode system is inserted in the electrodeposition solution, a thin film is deposited on a working electrode through an electrodeposition reaction, the thin film is flushed through deionized water and anhydrous ethanol correspondingly and dried in an air blasting drying oven, and thus the multi-element rare-earth-layer-shaped hydroxide thin film is prepared. According to the method, operation is easy, compared with a traditional method that powder is manufactured first and then the film is prepared, the thin film preparing method is greatly simplified, and meanwhile the influence of the powder morphology on the film forming quality is avoided; and the method provided by the invention is easy to operate, short inconsumed time and good in thin film quality.