Abstract: The influence of particle size, packing density, and particle size distribution on the thermal conductivity of aluminum nitride particle (AlN) filled resin composites was analyzed by the theoretical simulation method. We further used thermal conductivity data to investigate the thermal conductivity performance of composite materials. The simulation results showed that if the aluminum nitride particles are added into resin material, when the packing density of aluminum nitride particles is less than 10%, the thermal conductivity of the system is less than 0.6 W/(m·K). When the packing density of aluminum nitride is higher than 64%, the thermal conductivity of the system will be higher than 7.31 W/(m·K). Thermal conductivity pathways are crucial for the heat transfer. Some thermal conductivity pathways are formed between aluminum nitride particles at high-density stacking, which is useful for the heat conductivity. However, thermal conductivity pathways between particles cannot be formed at low-density stacking, resulting in lower thermal conductivity. According to the thermal conductivity of the resin of 0.3 W/(m·K), if a higher thermal conductivity is required, the particle packing density of aluminum nitride in the system needs to reach over 40%, preferably over 50%, so that the thermal conductivity of the composite material is higher than 2.5 W/(m·K). It will be time-consuming for measuring the thermal conductivity of aluminum nitride particle system under resin matrix conditions when the experimental sample number is relatively large. This work could provide a theoretical prediction before experimental work and the experiments could be reasonably carried out based on the theoretical results.