In order to solve the high brittleness of epoxy acrylate，low viscosity epoxyresin was firstly prepared by flexibility modification of E51 epoxy resin using polyethyleneglycol（PEG）with different relative molecular mass. The modified resin was then used to react with acrylic acid to prepare a low-viscosity epoxy acrylate resin. Next，succinic anhydride moiety was introduced into the epoxy acrylate resin，which was then neutralized bytriethylamine into a salt and emulsified with water to obtain the PEG-modified waterborneepoxy acrylate（PEG-WEA） emulsion. Finally the prepared emulsion was coated on a polyethylene terephthalate（PET） substrate. The PEG-WEA was characterized by Fourier transform infrared spectroscopy（FT-IR）and Gel permeation chromatography（GPC）to study the effects of the relative molecular mass of PEG on the particle size of the PEG-WEAemulsion，the kinetic behavior of the UV-curing process，the thermal stability，mechanical properties and the coatings properties. The results showed that，when the relative molecular mass of PEG was 600，the PEG-WEA emulsion had the smallest particle size（77. 96 nm），the double-bond conversion rate was improved，the UV-curing film presented good thermal stability and ductile fracture characteristics，the elongation at break was increased by 7. 54%. At the same time，the hardness of the coating after curing was up to 3H，the flexibility was 1 mm，and the adhesion was 2 level.