Polyethylene (PE), is a polymer formed by carbon-carbon single bonds, is a very stable material with a very slow degradation rate. In this paper, polyethylene films bag type were exposed to UV-B radiation (320-280 nm) at different exposure times (2 to 12 days). The UV radiation effects on PE samples were characterized using infrared spectroscopy with attenuated total reflectance (ATR). The vinyl group formation indicates the PE degradation. These chemical groups have IR absorption in 900-1300 cm-1; additionally the degree of crystallinity increase with the increasing of the exposure time. The experiment showed significant changes in PE molecular structure.