Abstract: Considering the axial temperature profile in CVD reactor, and based on the chemical reaction, nucleation, growth and coagulation of AlN UFP synthesis process by chemical vapor reaction, a one dimentional process model of particle size and distribution was established. To the AlCl_3-NH_3-N_2 system, the process properties of AlN particle formation and the effects of prosess parameters on AlN particle size and distribution were studied. The chemical reaction rate, nucleation rate and growth rate were strongly influenced by the axial temperature profile. The AlN particle size decrased with deceasing of AlCl_3 concentration and incrasing of total flow rate, and the AlN particle size distribution increased with increasing of total flow rate.