The invention relates to a synthesis method of an amino acid quaternary amino carboxylate, and belongs to the technical field of compound synthesis. The synthesis method comprises: dissolving 1 mole of an alkali metal hydroxide in a volatile organic solvent with a temperature of 20-30 DEG C to obtain a solution A; dissolving 1 mole of double chain quaternary amino ammonium halide or single chain quaternary amino ammonium halide into a volatile organic solvent to obtain a solution B; mixing A and B, and removing insoluble substances to obtain a solution C; dissolving acetylated amino acid in a volatile organic solvent until the obtained solution contains 1 mole of the acetylated amino acid anions so as to obtain a solution D; and mixing C and D, and removing insoluble substances and the volatile organic solvents to obtain the product. According to the present invention, the synthesis steps are simplified, the organic reagents with characteristics of low toxicity, easy recovery and easy treatment are used, and the purity of the amino acid quaternary amino carboxylate is improved.