Polymer nanoemulsion was prepared by high shear emulsion polymerization and its particle diameter was determined. The results showed that the particle diameter reduced with the increase of reaction temperature, initiator concentration, water content and stirring speed. The optimal ratio of constituents of nanopaints each to other was obtained by orthogonal factorization experiments, and the nanopaint with appropiate viscosity and excellent storage stability was prepared when it contains 0.2% of dispersant, 4.7% of alkaline swelling polyacrylate emulsion thickener and 1.4% of nonionic associative polyurethane thickener.