Abstract: Modified titanium sol was prepared by sol-gel method, using -methacryloxypropyl trimethoxy silane (KH-570) as modifying agent, and the modified titanium sol/acrylate composite emulsion with a core-shell structure was synthesized through the addition of modified titanium sol to the polymeric latex prepared from methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (AA), styrene(St）and hydroxyethyl methacrylate (HEMA) by semicontinuous seed emulsion polymerization and pre-emulsification. The influence of the emulsifying system, the amount of hydroxyl monomer, the content of modified titanium sol on the stability of the emulsion polymerization and the properties of emulsion were investigated, and the copolymer emulsion was characterized by FTIR 、DSC、GPC and SEM. Results showed that the latex particles had the regular spherical structure, and the average diameter of the particles was about 200 nm. The prepared emulsion had optimal stability and water repellency when the reactive emulsifiers SR-10 was selected, and the mass content of modified nano-TiO2 sol and hydroxyl monomer were 5% and 20%, respectively.