The aqueous styrene-acrylic water dispersion with a core-shell structure was obtained from ethenylbenzene (St), methyl methacrylate (MMA), butyl acrylate (BA), methacrylic acid (MAA) and 2-hydroxypropyl methacrylate (HPMA) by semi-continuous solution and phase inversion emulsion polymerization. The structure, thermal stability, colloidal structureof the acrylate copolymer was characterized by fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), transmission electron microscope (TEM), respectively. Moreover, the emulsifying performances and varnish film properties of aqueous styrene-acrylic water dispersion were discussed and the synthetic conditions were also optimized. The results showed that the aqueous styrene-acrylic water dispersion presents excellent stability and outstanding varnish film properties, the FT-IR and TGA of the polymer are consistent with the design structure,when mass ratio of methacrylic acid (MAA) in the core shell is 2:8, the mass fraction of MAA was7.5%, the mass fraction of 2-hydroxypropyl methacrylate (HPMA) was10.0%, St:MMA mass ratio is 3:1, The copolymer emulsion particle could reach 259.65nm, viscosity 381.5mPa?s, the filming hardness was 72.4?, tensile Strength 1.422MPa, elongation at break 59.355%, the filming water resistance time could approach 90h, and the adhesion level was 1.