Abstract: The influence of alumina particle size, packing density and particle size on the thermal conductivity of the system was analyzed by finite element numerical simulation. The simulation results show that the thermal conductivity of the system is lower than 0.5 W/(m·K) when the packing density of alumina particles is less than 10% under the resin matrix condition. When the packing density of alumina is higher than 65%, the thermal conductivity will be higher than 4.11 W/(m·K). This is because in high-density stacking, some thermal conduction paths are easily formed between alumina particles due to interface contact, which will be helpful to heat transmission. In low-density stacking, the particles are filled with resin. The thermal conductivity of resin is lower than alumina, and the heat transmission speed is slow. Compared with the thermal conductivity, 0.3 W/(m·K), of the resin, if higher thermal conductivity is required, the packing density of alumina should be higher than 60%.