Aluminum nitride (AlN) has excellent thermal property, but the thermal conductivity is low in practical use, so sometimes additives will be employed to improve the properties of AlN. Nano‑carbon materials have a finer size and higher thermal conductivity, which may enhance the sintering property and thermal property of AlN, making them suitable as excellent additives to improve properties. In the experiment, different nano‑carbon materials were added in AlN, after that the composites were obtained by hot-pressed sintering, and then the microstructure and thermal conductivity of the composites were studied. The results showed that the microstructure of AlN showed certain variations after adding nano‑carbon materials, reflecting changes in grain shape and grain size, as well as increased impurities. Furthermore, the closer the dimension and shape of nano‑carbon materials were to AlN, the better the effect of microstructural optimization. The thermal conductivity of AlN reduced following the addition of nano‑carbon materials due to excessive residual carbon and mixed iron components. Among them, the AlN reinforced by three-dimensional diamonds had the highest thermal conductivity, which can reach 107 W·m⁻¹·K⁻¹ at ambient temperature, compared to other nano‑carbon materials.