Provided is a method for preparing a β-amino phosphonic acid derivative comprising the following steps : dissolving an N-(aryl vinyl)benzamide, a dialkyl phosphite, a manganese acetate and a potassium carbonate in a solvent; reacting at room temperature to obtain a (2-benzamido-1-aryl vinyl) dialkyl phosphonate derivative; and electrolytically reducing the compound to obtain the β-amino phosphonic acid derivative. The N-(aryl vinyl)benzamide derivative is used as a starting material, and the raw materials are easy to obtain and are of many different types. The synthetic route is short, the reaction conditions are mild, the reaction operation and the post-treatment process are simple, the production is convenient, and the method is suitable for large-scale production.