In this paper, aluminum nitride (AlN) films have been successfully synthesized by taking solid AlCl 3 as the source of atomic aluminum, with negative bias assisted catalytic chemical vapor deposition (Cat-CVD) on Si(100) substrate at low temperatures. Nitrogen (N 2 ) and hydrogen (H 2 ) were used as gas precursors. The results show that by using AlCl 3 as the aluminum source AlN films with preferential orientation can be obtained under negative bias assistance by Cat-CVD. The effects of the bias during the deposition process are discussed in details.