Nanocrystal aluminum nitride (AlN) powders were obtained by the chemical vapor deposition (CVD) process via the AlCl3–NH3–N2 system at 1323 K with various total flow rates. The morphology and formation mechanism of the synthesized AlN powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It has been shown that all of the obtained powders exclusively belong to the single-phase AlN and do not depend on the variation of the total flow rate of the 1 : 1 molar ratio of the gas mixture of NH3/N2. On the other hand, the crystal shapes were affected by the position of the entry/mixing of the reacting gases of AlCl3 and NH3. The average crystal size of the AlN powders was decreased from 35.0 to 12.5 nm as the gas-mixture flow rates were increased from 200 to 800 cm3/min. A crystal growth model of the AlN powders has been proposed for the stages of the adsorption/desorption rates in the inlet zone of the reacting gases→AlN formation→crystal growth→crystal agglomeration.