Composites of Low-density polyethylene (LDPE) containing 1–5 wt% of Si/SiO 2 core/shell nanoparticles were fabricated by ball milling method. The neat LDPE and its composites were characterized by several experimental techniques such as DSC, SEM, BDS, AC breakdown, and erosion test to better understand the effects of Si/SiO 2 nanoparticle on thermal and dielectric properties of the composites. The results showed that the dielectric permittivity increased smoothly with a rise of Si/SiO 2 particle content in the concentration range studied. The real and loss parts of permittivity decreased and increased with temperature, respectively. The resistance of the composites to erosion due to partial discharge was significantly improved by adding Si/SiO 2 nanoparticles. The results have demonstrated that ball milling was an effective method for producing relatively homogenous LDPE Si/SiO 2 up to 4 wt% nanoparticle filler content with relatively high dielectric strength.