AlN (Aluminum Nitride) thin films have been prepared with reaction between Al and nitrogen under the conditions of excimer laser irradiation of an aluminum target and nitrogen discharge the while. The effect of laser energy density, substrate temperature, and gas-discharging on the composition and construction of the films was discussed. The stoichiometrical preferred-orientation AlN (100) polycrystalline films were deposited on Si (100) wafers with DE=1.0 J*cm-2, PN2=13.333 kPa, Tsub=200℃, V=650 V, f=5 Hz, and dS-T=4 cm. The testing results show the band gap, the resistivity and the breakdown electric field of the films are 6.2 eV, 2×1013 Ω*cm and 3×106 V*cm-1 respectively.