The invention relates to a preparation method of a salt-resistant amphoteric polycarboxylic acid high performance water reducer. By taking an unsaturated cation quaternary ammonium salt monomer, an unsaturated small monomer, an unsaturated initiator, a transitional metal complex as main raw materials, the salt-resistant amphoteric polycarboxylic acid high performance water reducer is synthesized by self-polymerization and grafted copolymerization, that is, the preparation method comprises the following steps: by taking the unsaturated cation quaternary ammonium salt monomer as a reactant, carrying out atom transfer radical polymerization (ATRP) in a system composed of the unsaturated initiator and the transitional metal complex to obtain a cation large monomer; and carrying out free radical grafted copolymerization on the unsaturated small monomer under the action of an initiator and a chain transfer agent. A molecular structure is designed and synthesized creatively based on a principle of conventional free radical polymerization and ATRP. The prepared water reducer has the advantage of keeping good dispersity in a high concentration salt condition and is simple in process, controllable in process and energy-saving and environment-friendly, and cationization substitution of a conventional polyether side chain is achieved.