The high quality polycrystalline AlN thin films have been deposited on the (100) and (111) Si substrates, the orientation relation between films and substrates was AlN(100)∥Si(100), AlN(110)∥Si(111) respectively. The AlN films have low residual stress and well thermal stability. The experimental result shows that the residual stress of AlN films prepared with 100×133.33 Pa nitrogen pressure and 650 V discharge-voltage was lower than 3 GPa. The infrared spectrum of the AlN films after annealed for 3 hours at 500℃ in pure oxygen atmosphere displayed the nonexistence of Al2O3. And the investigation of AlN/Cu dual-layer film showed the positive effect of AlN thin films on the protecting of metallic films.