With the modernization of electronic devices, the requirements for thermal conductivity and heat dissipation materials for high-power electronic devices are increasing, and the study of new thermally conductive materials for electronic packaging is of great importance to solving this "hot spot" problem. This paper describes the use of high-temperature sintering of micron-sized alumina, the bonding of sintered branched alumina (b-Al2O3) to an epoxy resin (EP) matrix, and the preparation of b-Al2O3/EP composites. When the filling mass fraction of b-Al2O3 was 60%, the thermal conductivity of the composites reached 0.86 W/(m. K), 570% improvement in thermal conductivity compared to pure epoxy resin, and the resistivity of the composites was 2.2x10(13) Omega center dot m. The geometric model of representative units was established by a stochastic algorithm, the model restores the random distribution state of filler particles in the epoxy resin matrix, the errors due to the artificial setting of the geometric model are reduced; and the internal thermal conductivity transfer process of the composite is analyzed by finite element simulation. The efficient thermal conductivity of the b-Al2O3 thermal channel is revealed, and the better thermal conductivity and electrical insulation properties of b-Al2O3/ EP are demonstrated.