Abstract: Emulsion polymerization was adopted to synthesize the surface sizing agent with polystyrene,acrylic acid, butyl acrylate as monomers and enzymeconverted starch as a emulsifier, using PlackettBurman and total divisor design as the design of experiment(DOE). The results showed that dosage of evocation agent(A), reaction temperature(B), charging time(C) and the interaction(AC) between dosage of evocation agent and titration time were the key factors affecting the surface strength(S) of paper. The relationship among them was expressed with a mathematics model:S=-17375 0+196259A+15B+48375 0C-4125AC and the experiment confirmed its correct ness. The optimum reaction conditions of enzyme was 80 ℃,10 min and the mass ratio of it to monomer quality was 1〖DK〗∶1. The optimum synthesis condition was 2 ％ acrylic acid,the ratio of polystyrene to butyl acrylate 6〖DK〗∶1 and the mass ratio of H2O2 to FeSO4 1〖DK〗∶1. The surface sizing agents solid content was 2613 ％, viscosity was 283 mPa〖DK〗·s and the glass transition temperature was 7072 ℃.