Abstract: AlN films were synthesized on Si substrates by pulsed laser deposition（PLD）.X-ray diffraction（XRD） spectra show that the films have a（002）-oriented hexagon wurstite crystalline structure and the crystallinity becomes better with higher substrate temperature.Current-voltage（I-V）,capacitance-voltage（C-V） and polarization measurements demonstrate that the room-temperature grown sample has a breakdown field of 2.5MV/cm,and also a clear polarization hysteresis.Based on the intrinsic large spontaneous polarization in crystalline AlN and the large dynamic charge density in the samples,a dynamic charge model is proposed to interpret the observed polarization,which is due to redistribution of dynamic charges.Therefore it′s different from ferroelectric materials.