A method for producing an amino acid liquid fertilizer from waste feathers includes: acquiring an enzymatic hydrolysate by performing enzymolysis on feather powder with a complex enzyme; adding acid protease to the enzymatic hydrolysate for enzymolysis; and acquiring the amino acid liquid fertilizer by performing enzyme inactivation on a filtrate acquired by performing filtering after enzymolysis is completed, wherein the complex enzyme includes keratinase and amino acid peptidase. By adopting this method, the enzymolysis rate of the feathers reaches 80% or above and the prepared amino acid liquid fertilizer contains various kinds of amino acids (17 amino acids); and the content of the amino acid can reach 10.12% (by mass fraction) or above and the content of small peptide reaches 9.39% (by mass fraction), which reach the Chinese standard of the amino acid liquid fertilizers without concentration. Thus, the environmental-friendly amino acid liquid fertilizer can be prepared.