In this study, we optimized the preparation of 100–160 nm monodispersed SiO2 nanoparticles and, through doping, investigated their effects on the physical properties of a water-based acrylic-amino varnish. First, using a non-fixed point feeding technique based on the half-batch sol-gel method, we enhanced the yield of small-sized monodispersed SiO2 nanoparticles. To reduce the cost of production and organic-matter pollution, we assessed certain solution parameters including tetraethyl orthosilicate (TEOS), ethanol (ETOH) and ammonia in a single-reaction system. We found that the gloss, clarity, hardness, adhesion, and other physical properties of the acrylic-amino varnish were successfully enhanced through an addition of 1.2 % SiO2 nanoparticles.