By cyclic vapor-solid (VS) process, aluminum nitride (AlN) clusters were formed on the surface of polycrystal AIN substrate. These clusters can be classified into three types: single crystal, polycrystal and particle clusters. it was observed that the single crystal had similar morphology as crystallinity suggests, while the polycrystal was configured by terrace, which again was constructed by plate-like AlN single crystals. Particle clusters were actually a porous network of AlN particles. Further investigation showed that the formation of clusters was greatly influenced by two factors: polycrystal AlN substrate and repeated heat treatment. Based on the observed facts, a growth process of the clusters was discussed.