Abstract: The inorganic nano ZnO and montmorillonite (MMT) particles were doped in low density polyethylene(LDPE). The effects of inorganic nano particles on the dielectric properties LDPE were discussed. The nano ZnO/LDPE and nano MMT/LDPE composites with different crystal habits were prepared using melt blending polymerization with different cooling methods. The samples were characterization using FTIR, polarizing microscopy (PLM), SEM, DSC and thermally stimulated current (TSC), and the alternating curren breakdown characteristics of nano ZnO/LDPE and nano MMT/LDPE composites was studied. The results indicate that doping proper mass fraction of the inorganic nanoparticles touched by the surface can avoid the agglomeration effectively. It can raise the crystallization rate and improve the crystalline texture of nano ZnO/LDPE and nano MMT/LDPE composites. The inorganic nano particles doping would increase the density and depth of LDPE. Inside the sample would form the interface "localization state" owing to the charge carrier is trapping. The breakdown field strength of nano ZnO/LDPE and MMT/LDPE composites prepared by oil cooling are 13.6% and 14.4% higher than that of the composites prepared by natural air cooling. When the content of the nano particles doped is 3wt%, the breakdown strength of the composites appeares the highest values; the breakdown strength of ZnO/LDPE composite is 0.68% higher than that of MMT/LDPE composite. The conductivity experimental results show that the nano ZnO/LDPE composite conductivity is relatively lower than that of MMT/LDPE composite. The dielectric properties tests show that the nano ZnO/LDPE and MMT/LDPE composites dielectric constant decreases, and the tangent value of dielectric loss angle is improved in the range of 1-10⁵ Hz test frequency.