In this work, an efficient carbothermal reduction-nitridation strategy was rationally designed and delicately tailored to directly synthesize spherical granules of aluminum nitride. Effects of processing parameters, such as N-2 pressure, additives and temperature on the nitridation ratio, especially on the morphologies of the AlN granules were elaborately investigated. The experimental results showed that the elevated N-2 pressure of 0.9MPa and additives of CaF2 and Y2O3 greatly favored for forming micrometer-sized AlN granules with smooth spherical appearance. More significantly, the underlying formation mechanism of spherical morphology and large particle size was also attentively put forward.