In order to introduce an isocyanate (NCO) functional group into low density polyethylene (LDPE), grafting of 2-hydroxyethyl methacrylate (HEMA) combined with isophorone diisocyanate (IPDI) on to LDPE was carried out in solution using a radical initiator. The spectra of infrared (i.r.) and proton nuclear magnetic resonance for HEMA combined with IPDI showed that the hydroxyl group of HEMA and the NCO group of IPDI were reacted to form urethane, and the secondary NCO group preferentially reacted over the primary NCO group. From the i.r. spectra of the grafted LDPE, it was found that NCO groups were introduced into LDPE. Thermal stability of the grafted LDPE was investigated by differential scanning calorimeter analysis, and rheological values were observed to evaluate processability.