The invention discloses a method for preparing a lanthanum phosphate or rare earth doped lanthanum phosphate film through electrodeposition, which comprises the following steps of: (1) cleaning ITO (Indium Tin Oxide) conducting glass 2-3 times with acetone, cleaning the ITO conducting glass with deionized water for 10-30 min in an ultrasonic cleaner, activating the ITO conducting glass in a 10 vol% saltpeter solution for 10-30 s, and cleaning with deionized water for later use; (2) adding a sodium phosphate solution into a 0.005-0.5 mol/L complex solution of ethylene diamine tetraacetic acid and lanthanide ions, and regulating the pH value to 4-6 to obtain an electrolyte for later use; and (3) placing the ITO conducting glass used as a working electrode, a platinum electrode used as a counter electrode and a calomel electrode used as a reference electrode in the electrolyte for electrodeposition to obtain the lanthanum phosphate film, wherein the positive deposition potential relativeto the calomel electrode is 1.2-1.8 V. The invention has the advantages of simple equipment, low cost, normal pressure and low temperature. The method not only is applicable to scientific research, but also is hopeful for realizing large-scale industrial production.