The invention relates to a styrene-acrylic composite emulsion, particularly preparation of silicon-containing styrene-acrylic composite emulsion nanoparticles, which comprises the following steps: 1. pre-emulsification: adding an emulsifier and a seed monomer to carry out pre-emulsification; 2. adding an initiator to carry out seed emulsion polymerization; and 3. adding the rest of monomer, emulsifier, initiator and silane coupling agent into the polymerization system to carry out polymerization, thereby obtaining the silicon-containing nano polyacrylate composite emulsion. The whole preparation process has a definite procedure and is simple to operate. By adopting free radical copolymerization, the silicon-containing acrylates are introduced into the styrene-acrylic polymer emulsion by copolymerization, thereby preparing the monodisperse nano silicon-containing styrene-acrylic emulsion. The product integrates the advantages of silicon and nano styrene-acrylic emulsion. The monodisperse styrene-acrylic composite emulsion has small-size effect, surface effect, quantum size effect, macroscopic tunneling effect and the like. Therefore, related materials have electric, magnetic, thermal and optical sensitivity, and the surface stability is obviously different from that of micron particles. The invention relates to the application fields of chemistry, materials, biology, medicine, textile, paper making and the like, and has high use value.