The invention discloses a water-based polyacrylate emulsion and a preparation method thereof. At present, there are few reports on the emulsions of large particle size, low viscosity, and high solid aqueous polyacrylates that meet various stability and application requirements. In the present invention, one or more of butyl acrylate, ethyl acrylate, and isooctyl acrylate are used as soft monomers, and one or more of methyl methacrylate, styrene, methyl acrylate, and acrylonitrile are used as soft monomers. Hard monomer, one or more of methacrylic acid, acrylic acid, itaconic acid, acrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, N-methacrylamide The first is a functional monomer, the compound emulsifier and the reactive emulsifier construct an emulsification system, the redox system initiator is used as the initiator, and the polymerization process of high-shear pre-emulsification and seed emulsion is used to obtain large particle size, high solid content and Low viscosity aqueous polyacrylate emulsion.