In order to apply isocyanate (NCO) functional group to the reactive compatibilization of nylon 6/LDPE blends, low-density polyethylene grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (LDPE-g-HI) was prepared. From the results of infrared spectra and Molau test, it was found that the chemical reactions of NCO and amino end group occurred during the melt blending. In view of the blend morphology, the dispersions of the nylon 6/LDPE-g-HI blends were very fine over the nylon 6/LDPE blends and the junctions between the phases appeared at the interface of the 50/50 nylon 6/LDPE-g-HI blend. For the nylon 6/LDPE-g-HI blends, a strong positive deviation from the mixing rule was observed in rheological measurements, as a result of the chemical reaction.