The invention discloses amphiprotic amphiphilic leather retanning fatting agent and a preparation method of the amphiprotic amphiphilic leather retanning fatting agent. The constituent of the amphiprotic amphiphilic leather retanning fatting agent is (methyl) crylic acid-N-
alkyl diene propyl amine-diallylamine terpolymer. According to the preparation method of the amphiprotic amphiphilic leather retanning fatting agent, N-
alkyl diene propyl amine is firstly prepared, then the N-
alkyl diene propyl amine, diallylamine, and (methyl) crylic acid are adopted for a free radical copolymerization reaction under the acidic condition to obtain an aqueous dispersoid containing the (methyl) crylic acid-N-alkyl diene propyl amine-diallylamine terpolymer, the
solid content of a product is adjusted to 15-20% with water, and the amphiprotic amphiphilic leather retanning fatting agent is obtained. The molecular structure of the amphiprotic amphiphilic leather retanning fatting agent contains carboxyl of negative ions and
tertiary amino of positive ions, and the
polymer can display different electrical properties under different conditions of potential of
hydrogen (PH), meanwhile the
polymer contains alkyl of a
long chain, and functions of
lubrication fibers can be achieved. The
polymer has the function of retanning, fatting and
dyeing assistance at the same time, physical and mechanical properties of processed crust leather, such as tensile strength, fullness, softness and elasticity, are all improved, the surface of the processed crust leather is strong in
lubrication feel and comfortable in hand feel, and the leather has a good waterproof performance.