High thermal conductivity composites with ideal electrical properties have a wide potential application of electronic packaging systems in aerospace, electrical and electronic fields. Hexagonal boron nitride (h-BN) has been widely used in heat conduction systems due to its good insulation and thermally conductivity. However, its application has been limited due to its surface inertness and low strength. In this work, dopamine (DA) was used to provide a polymer coating (PDA) in the hexagonal boron nitride (h-BN) surface to improve its uniform dispersion and interfacial compatibility in the polymer matrix (A-ph/CE). Polymer nanocomposites with different nanofiller loadings were prepared by simple curing casting procedure. Among them, the thermal conductivity of A-ph/CE/[email protected] nanocomposites with 20 wt% [email protected] increases to 0.71 W/m⋅K. The thermal conductivity of nanocomposites was predicted by using the classical equation Agari model. With the nanofiller amounts increasing, the thermal stability of the nanocomposites also improved. The thermal decomposition and Tg with A-ph/CE/[email protected] nanocomposites with 20 wt% [email protected] increase to 350.8 °C and 339.9 °C, respectively. And its dynamic storage modulus reaches 7390 Mpa. And the prepared composites had ideal dielectric properties. The dielectric constant and dielectric loss of 20 wt% A-ph/CE/[email protected] nanocomposites at 1000 Hz were 5.72 and 0.0148 respectively, the volume resistivity was 4.08 × 108 Ω cm, and dielectric breakdown strength was 61.6 kV/mm. The nanofiller ([email protected]) reinforced polymer nanocomposites (A-ph/CE/[email protected]) prepared in this work has good thermal conductivity, ideal electrical properties, and excellent thermal stability, etc., which has great potentiality in the demanding field of electronic packaging.