The invention discloses a preparation method for synthesizing a thickening agent by acrylic ester. The thickening agent synthesized by acrylic ester comprises crylic acid, acrylamide, 25 percent of ammonia water, a functional monomer, EDTA, deionized water, tasteless kerosene, 3<#> white oil, diallyl phthalate, ammonium persulphate, Span 80 and isomeric hexadecanol polyethenoxy ether, wherein the functional monomer is prepared from alicyclic amine polyethenoxy ether, methyl methacrylate, nitroxide free radical pipradrol and sodium methoxide. The preparation method synthesizes a special weak cation type (methyl) acrylic ester functional monomer by adopting an ester exchange method, and the functional monomer and vinyl monomers of the acrylic acid, the acrylamide, and the like are adopted to synthesize a textile printing thickening agent by adopting inverse emulsion polymerization. The thickening agent has the characteristics of high thickening capacity, strong electrolyte resistant capacity and good water-retaining property.