Abstract: Zinc oxide（ZnO） precursor（namely basic zinc carbonate） was first synthesized via homogeneous precipitation method,then ZnO nanoparticles with different diameter were made by calcination of the precursor at different temperatures.ZnO/Epoxy nanocomposites were prepared from transparent epoxy （EP-400） and as-prepared ZnO nanoparticles via in situ polymerization method.The structural properties of the as-prepared nanoparticles were investigated by using TG,XRD and TEM,respectively.Optical properties of ZnO/Epoxy nanocomposites were studied by UV-VIS spectrophotometer.The results show that the selection of a proper particle size is important to obtain high UV-light shielding efficiency.Since the blue shift of UV-light shielding will occur as the ZnO particle size decreases and the increasing content of ZnO with proper particle size can improve the UV-light shielding effect.The transmittance of visible light decreases while ZnO content and ZnO particle size increase simultaneously.The ZnO/epoxy nanocomposites containing 0.07wt% ZnO nanoparticles with the mean particle size of 27 nm show excellent UV light shielding efficiency and high visible light transparency,which fulfils the desire for packaging materials of LED.