AlN thin films with(100) preferential orientation were prepared on Si(100) substrates(including Au conductive layer) by radio frequency(RF) magnetron sputtering technique.The effects of gas pressure and sputtering power on the preparation of the(100) oriented AlN film are studied.The structure properties of the film are analyzed by X-ray diffraction(XRD).And the results show that the(100) oriented AlN film is easily formed at higher gas pressure and lower sputtering power.The surface topography and piezoelectric properties of the film are characterized by piezoresponse force microscopy(PFM).It is found that the piezoelectric properties of the(100) oriented AlN film are mainly observed in the direction parallel to the surface of the film.