Au films of various thicknesses are fabricated by ion-beam sputtering with different coating parameters on quartz and K9 substrate which are processed with different cleaning procedures. Their reflectivity is measured continuously in a broad vacuum ultraviolet range. It is indicated that the auxiliary ion-beam source and the film thickness impact significantly on the reflectivity. Substrate material and cleaning procedure also affect reflectivity of Au film to some extent. Ion-beam bombardment of substrate before deposition can significantly enhance the reflectivity and adhesion of films. The optimal film thickness for the highest reflectivity connects closely with substrate material and coating techniques. For quartz substrate processed by ion bombardment pre-deposition, the optimal film thickness is about 30 nm, and the reflectivity of quartz is higher than K9. The use of auxiliary ion beam source influences the optimal film thickness for the highest reflectivity, and the influence is larger for K9 substrate.