The crystalline AlN thin film was fabricated on Si(100) substrates by plasma-enhanced atomic layer deposition. Its growth rate was illustrated by spectroscopic ellipsometer. And the surface morphology, crystal structure and composition were characterized by atomic force microscopy, X-ray diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Results show that the lowest temperature for deposition of the crystalline AlN thin film is 200 ℃, and the film coverage on the substrate surface is continuous and homogeneous. The film prepared with a homogeneous concentration distribution is polycrystalline with a hexagonal wurtzite structure. High resolution Al2p and N1s spectra confirm the presence of AlN with peaks located at 74.1 eV and 397.0 eV, respectively.