AlN thin films were deposited by the direct current (DC) reactive magnetron sputtering technique on Si (111) substrates at different sputtering power. The X ray diffraction (XRD), field emission scanning electron morphology (FESEM) and atomic force microscope (AFM) were employed to characterize the films’ morphology deposited at different sputtering power. The results show that within a certain range, the film thickness, crystal grain size and surface roughness values increased with increasing the input sputtering power; the preferential c axis orientation has been improved significantly with increasing input sputtering power and it has been become optimal when the input power was up to 120 W.