The invention relates to a preparation method of a temperature responsive comb-like structured polycarboxylic acid. By using acrylic ester, a temperature responsive monomer and the like as raw materials, a polycarboxylic acid material is prepared through steps of autopolymerization, graft copolymerization and hydrolysis. The preparation method comprises the following specific steps: acrylic ester,which is used as a reaction monomer, undergoes polymerization under the action of an initiator and a chain transfer agent to generate polyacrylate with controlled molecular weight; then, polyacrylateand the temperature responsive monomer are subjected to graft copolymerization to obtain a graft copolymer with the acrylic polymer as the a main chain and the temperature responsive polymer as a side chain; and finally, the graft copolymer undergoes hydrolysis to prepare the comb-like structured polycarboxylic acid with polyacrylic acid as the main chain and the temperature responsive polymer asthe side chain. By main chain polymerization before side chain grafting, polycarboxylic acid with the intelligent responsive side chain is successfully designed and synthesized. The reaction processis convenient and controllable, and is energy-saving and environmentally friendly. The product shows excellent temperature responsive behavior and multi-effects of inhibiting shrinkage of cement mortar, and has good market prospects and application value.