The invention relates to a method for preparing the aqueous emulsion of a polyacrylic acid, which is characterized in that: based on the total weight, the aqueous emulsion of the polyacrylic acid comprises the following components in percentage by weight: 10.0 to 20.0 percent of arylic acid-methacrylate copolymer, 10.0 to 20.0 percent of inorganic salt, 3.0 to 8.0 percent of isopropyl alcohol, 1.0 to 2.0 percent of stabilizing agent, 0.05 to 0.15 percent of initiator, 0.0 to 0.2 percent of aid and the balance of water. The method comprises the following steps of: dissolving an arylic acid and methacrylate into the water in determined proportion, neutralizing the mixed solution with sodium hydroxide until a pH value is 5 to 7, adding the inorganic salt, the isopropyl alcohol, the stabilizing agent, the initiator and the aid in determined proportion for uniform mixing, introducing nitrogen, removing oxygen and performing stirring reaction under the protection of the nitrogen at 50 DEG C for 16 hours to obtain the aqueous emulsion of the polyarylic acid of the invention. The aqueous emulsion of the polyarylic acid is stable milky liquid prepared from a water-soluble polymer by taking the water as a medium, and has the advantages of low apparent viscosity, environmental friendliness and convenient use.