The halogen-free flame retardant PE-HD for cable jackets was modified with maleic anhydride grafted polyethylene (PE-g-MAH). The mechanical, rheological, thermal properties and the oxygen index of the alloy were determined, the fractured surface was investigated using SEM. It was found that the PE-g-MAH increased the interaction between the PE-HD and the flame retardant, and promoted the dispersion of the latter in the former. The toughness of materials was also improved.