Abstract: Due to the poor heat transfer performance of traditional epoxy composites, it is difficult to meet the development needs of electrical and electronic fields. The establishment of a three-dimensional continuous heat transfer network in epoxy composites is an important method for significantly improving its thermal conductivity. In this paper, boron nitride (BN) with excellent insulation properties was utilized as a raw material, and a new scheme combining gel method and sacrificial template method was employed to construct a three-dimensional BN network. Most of the auxiliary materials were removed by high temperatures to ensure the purity of the insulation network, and epoxy composites were obtained after vacuum impregnation. The test results demonstrate that, under the same filling load, the thermal conductivity of the 3D-BN/EP composites prepared by this scheme is significantly higher than that of the BN/EP composites prepared by traditional doping scheme, with the highest thermal conductivity reaching 1.50 W/m·K, which is 650% higher than that of pure epoxy resin. Additionally, the 3D-BN/EP composites exhibit superior dielectric properties(ε_r < 4.4, tanδ < 0.01) over a wide temperature range (0~100 ℃) and electric field strength range (10³~10⁶ V/m), with dielectric properties gradually increasing with packing load due to fewer impurities and fewer pore defects. The AC breakdown field strength of 3D-BN/EP composites is consistently maintained at a high level. Furthermore, comsol finite element simulation confirms that constructing a continuous heat transfer path can effectively improve the heat transfer capacity of BN/EP composites.