In the present work, response surface methodology (RSM) based on box Behnken design (BBD) was used to optimize preparation of LDPE/TiO2 nanocomposites by ball milling process. Low density polyethylene (LDPE) matrix was reinforced by titanium dioxide (TiO2) nanoparticles. Interaction effects of three individual variables, namely TiO2 nanoparticles content, milling time, and specimen thickness on nanocomposites dielectric strength were investigated using BBD. The results showed that TiO2 nanoparticles content and specimen thickness had major influence on performance improvement of dielectric strength. Numerical optimization was applied to determine the optimum factors for maximum dielectric strength. It was found that the optimum dielectric strength was 84.76 kV mm−1, when the process parameters were TiO2 content of 3.00 wt%, milling time of 39.90 min, and specimen thickness of 1.00 mm.