Preparation and characterization of high solid acrylic based polyurethane/nano-silica coatings and acrylic latex/nano-silica coatings were investigated. For acrylic based polyurethane, nanocomposite polymer coatings with different nano-SiO2 particles embedded were prepared via in situ polymerization or blending method. For acrylic latex, nanocomposite polymer coatings with nano-SiO2 particles embedded were prepared by blending via high shear stirring or ball milling and in situ polymerization. The mechanical and optical properties of the nanocomposite polymer coatings were studied intensively using pendulum hardness tester, scanning probe microscope (SPM), instron testing machine, dynamic mechanical analyzer (DMA), transmission electron microscope (TEM), and ultraviolet-visible (UV-VIS) spectrophotometer. The coatings with micro-SiO2 embedded were also investigated for comparison with the coatings containing nano-SiO2. The results showed that the macro hardness, micro hardness, and scratch resistance were obviously improved via addition of nano-SiO2. The tensile strength was also enhanced with the increasing content of nano-SiO2. The UV absorbance in the wavelength of 290-400 nm increased as nano-SiO2 content increased but did not change with micro-SiO2 particles. Acrylic/nano-SiO2 composite latex showed that different preparation method could cause different dispersion of nanoparticles in the polymer matrix.