Radiation effects on dielectric properties of low density polyethylene(LDPE) were investigated using the various measurements of FT-IR, gel content and elongation at break. FT-IR spectra showed that polar groups were comprised in LDPE due to radiation treatment. It was also confirmed that the formation of polar groups on LDPE caused the increased dielectric properties such as permittivity and tan $delta$. However, in this study, any evidence of decreasing permittivity was not found although the morphological change of LDPE could be identified from the increasing gel content and the decreasing elongation.