Dense MgO films for a protective layer of plasma display screen have been prepared by ion beam-assisted deposition. Properties of the deposited films and relationships between the deposition parameters and the properties have been investigated using X-ray diffractometry, scanning electronic microscopy and X-ray photoelectron spectroscopy (XPS). The deposited films exhibit mainly (200) preferable orientation. From the cross-sectional morphology, the density and the refractive index, it can be known that the MgO films prepared by ion beam-assisted deposition are much denser and more adhesive to substrate than the films deposited by electron beam evaporation. Ion energy, substrate temperature, growth rate and annealing treatment affect the orientation of the MgO films. The best crystallinity of the MgO films can be obtained for ion bombardment with energy of 1keV. With ion energy of 1keV, the orientation. of the MgO films becomes better for lower substrate temperature or growth rate. Annealing treatment in dry air is beneficial to the grain growth further.