The addition‐type liquid silicone rubber (ALSR) co‐filled with spheroidal Al2O3 and flaky BN was prepared by the mechanical blending and hot press methods to enhance the thermal, electrical, and mechanical properties for industrial applications. Morphologies of ALSR composites were observed by scanning electron microscopy (SEM). It was found that the interaction and dispersion state of fillers in the ALSR matrix were improved by the introduction of BN sheets. Thermal, electrical, and mechanical performances of the ALSR composites were also investigated in this work. The result indicated that the thermal conductivity of ALSR can reach 0.64 W m−1 K−1 at the loading of 20 wt% Al2O3/20 wt% BN, which is 3.76 times higher than that of pure ALSR. The addition of Al2O3 particles and BN sheets also improve the thermal stability of ALSR composites. Moreover, pure ALSR and ALSR composites showed relatively lower dielectric permittivity (1.9–3.1) and dielectric loss factor (<0.001) at the frequency of 103 Hz. The insulation properties including volume resistivity and breakdown strength were improved by the introduction of flaky BN in the ALSR matrix. The volume resistivity and characteristic breakdown strength E0 are 6.68 × 1015 Ω m and 93 kV/mm, respectively, at the loading of 20 wt% Al2O3/20 wt% BN. In addition, the mechanical characteristics including elongation at break and tensile strength of ALSR composites were also enhanced by co‐filled fillers. The combination of these improved performances makes the co‐filled ALSR composites attractive in the field of electrical and electronic applications.