This paper theoretically and experimentally investigates the reflective performance of Ir films in the vacuum ultraviolet wavelength region. Ir reflecting layers of different thicknesses on various substrates are calculated and fabricated by the ion-beam-sputtering technique. Their reflectance in the 115 nm to 140 nm wavelength region was measured continuously by a reflectometer located at the National Synchrotron Radiation Laboratory. The testing results show that the reflectance of Si substrates is quite sensitive to the deposited Ir layer thickness, while the reflectance on a quartz or a BK7 glass substrates is higher. The energy of the sputtering ion beam exerts a significant influence on the reflectance of the layer, and the postannealing can cause a substantial decrease in the reflectance. For normal incidence, the reflectance of an Ir film on BK7 glass can reach as high as 30%.