Abstract. Cu 6 PS 5 I-based thin films were deposited using non-reactive radio-frequency magnetron sputtering. Structural studies of thin films were performed by scanning electron microscopy, their chemical composition were determined using energydispersive X-ray spectroscopy. As-deposited thin films were irradiated with wideband radiation of Cu-anode X-ray tube at different exposition times. Optical transmission spectra of X-ray irradiated Cu 5.56 P 1.66 S 4.93 I 0.85 thin films were measured depending on irradiation time. The Urbach absorption edge and dispersion of refractive index for X-ray irradiated Cu 5.56 P 1.66 S 4.93 I 0.85 thin films were studied. It has been revealed the nonlinear decrease of energy pseudogap and nonlinear increase of refractive index with increase of X-ray irradiation time.