Abstract: SiO₂/polyacrylate composite emulsions ( Si/PAE) were prepared by polyacrylate emulsions (PAE) mixing with alkaline silica sol modified by a saline coupling agent and a co-solvent. The effects of kinds and amounts of co-solvent s on the sol-gel reaction and the properties of composite films were investigated. The results indicate that isopropanol is the best co-solvent and the optimal dosage is 10 wt% of the silica sol. The nano-granularity analysis and TEM photos show that co-solvents can make the silica particles distribute more evenly in the composite emulsions and reduce the average diameters of the Si/PAE. The FTIR spectra and AFM pictures indicate that co-solvents could induce the occurrence of sol-gel reaction of silica sol to form Si-based polymers on the surface of films during the film formation. Si/ PAE films display excellent properties besides high gloss and compact. TGA curves indicate that the Si/PAE films exhibit higher thermal stability than PAE.