LDPE and LLDPE were used as basic materials and nano-Mg(OH)-2 was added into them to prepared fire-retardant systems. The molding technological parameters and fire-retardant properties of the fire-retardant systems were studied. The result showed that when Mg(OH)-2 is added, the rotational speed of the screws increases; with the increase of Mg(OH)-2 content, the extruder pelletization temperature of materials gradually decreases; when the samples are molded, with the increase of Mg(OH)-2 content, the mold temperature slowly increases; when the addition of Mg(OH)-2 is more than 30%, the droplet phenomenon eliminates; and when the addition of Mg(OH)-2 is 50%, the fire-retardant level rise to FV-0.