Polyethylene materials are widely used in high voltage transmission lines and industrial production, polyethylene material because of its superior insulation performance, environmental friendly and high cost performance and become the cable insulation materials, in direct current field, however, space charge easily in the PE internal trap accumulation, result in higher local space charge, make the polyethylene material aging, breakdown, even in recent years, nanometer magnesia UG - join Mg50 particles can effectively inhibit the space charge injection, and nanometer magnesia add has become the main direction of current research.

　　In this paper, the influence of nanometer magnesium oxide doped polyethylene (mgo) on its electronic structure and electrical conductivity is discussed by means of the study of bulk phase structure system and double probe structure system.The polymer is common in high voltage power transmission cable insulation materials, such as polyethylene, crosslinked ethylene is more common in use, such as ways to improve the performance of composite materials, by adding inorganic material, montmorillonite, nano oxide particles, such as when a proportion of additives are added to the composite material, mechanical properties and electrical performance will be increase accordingly.

　　In 2006, the dielectric properties of LDPE/ magnesium oxide nanocomposites were studied. Under the condition of ac high voltage, the space charge behavior of LDPE/ magnesium oxide nanocomposites with different particle sizes of magnesium oxide nanoparticles was found in 2008, especially under the condition of high temperature and high power plant.The results show that the effect can be obtained by gradually increasing the number of nano-magnesium oxide particles between 30℃ and 60℃ in order to reduce the rate of electric field increase.In addition, in order to reduce the electric field distortion, also in order to reduce from the domain of charge injection, the use of nanometer magnesia particles also made the corresponding research on particle size of the order of magnitude, found that the nano-sized magnesium oxide particles significantly better than that of the micron grade magnesium oxide particles, when a small amount of magnesium oxide nanoparticles effect is more obvious when using on the substrate.

　　Adding nano-sized magnesium oxide to modify polyethylene assisted by EVA can significantly reduce the space charge accumulation problem. While solving the accumulation problem, it is also found that this modification can also improve the mechanical properties.When the additive amount of nano magnesium oxide is 2wt%, a better effect can be obtained.At this time of the nano magnesium oxide/LDPE composite material can effectively reduce the accumulation of space charge effect is significantly lower than single insulating polyethylene, the experimental results, the composite cathode charge density decreased to 2.5 in C/m3, the anode charge density decreased to 3.5 C/m3 in the breakdown of the direct current experiments, found that use of nanometer magnesium oxide doped LDPE breakdown voltage is greater than the doping of LDPE, and the largest increase to 18.2%, in the ac voltage breakdown experiments, got the same conclusion, and breakdown voltage with the temperature change, when the temperature rises breakdown voltage corresponding to the lower.