High transparent and UV-shielding poly (styrene)-co-poly(methyl methacrylate) (PS-PMMA)/zinc oxide (ZnO) optical nanocomposite films were prepared by solution mixing using methyl ethyl ketone (ME K) as a cosolvent. The films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis) spectra, high-resolution transmission electron microscopy (HR-TEM), and atomic force microscope (AFM). Cross-section HR-TEM and AFM images showed that the ZnO nanoparticles were uniformly dispersed in the polymer matrix at the nanoscale level. The XRD and FTIR studies indicate that there is no chemical bond or interaction between PS-PMMA and ZnO nanoparticles in the nanocomposite films. The UV-vis spectra in the wavelength range of 200-800 nm showed that nanocomposite films with ZnO particle contents from 1 to 20 wt % had strong absorption in UV spectrum region and the same transparency as pure PMMA-PS film in the visible region. The optical properties of polymer are greatly improved by the incorporation of ZnO nanoparticles. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1507-1512, 2010