Amino acid fertilizer with low salt and low proline content and preparation method thereof

The invention discloses an amino acid fertilizer with low salt and low proline content and a preparation method thereof. The amino acid fertilizer comprises the following raw materials: 20-30% of keratin, 3-5% of quick lime, 1.5-2% of triethanolamine, 1.5-2% of glycerol, 5-7% of phosphoric acid, 2-3% of copper nitrate and the balance of water. Keratin, glycerin, phosphoric acid and water are subjected to high-pressure and high-temperature hydrolysis, and then lime milk is added for normal-pressure hydrolysis; removing proline from the supernate of the hydrolysate, mixing with the lower turbid liquid, adding triethanolamine and phosphoric acid, continuously heating at normal pressure, filtering to remove solid precipitate, controlling the proline content to be less than or equal to 2.5% of the total amino acid content, and regulating to be neutral. When the amino acid fertilizer with low salt and low proline content is used as a foliar fertilizer, the osmotic pressure is low, the amino acid concentration can b