To improve the agglomerate phenomena of polarity nanosized MgO-filler in non-polar low density polyethylene (LDPE) matrix, in the composite (MgO/LDPE) master batch preparation process, adding a certain amount of ethylene-vinyl acetate copolymer (EVA), in order to improve the compatibility of nanoparticles and matrix materials. The dispersion states of MgO in the MgO/LDPE and EVA/MgO/LDPE composite material was evaluated by using scanning electron microscope (SEM), results shown that compared with MgO/LDPE nanocomposite, the dispersion of EVA modified MgO/LDPE is better and the agglomerate phenomena is not seen. DC breakdown tests shown that EVA modified MgO/LDPE compared with other several kinds of materials (LDPE; EVA/LDPE; MgO/LDPE and EVA/MgO/LDPE); the DC breakdown strength has improved significantly.