© 2020 Elsevier Ltd We report the X-ray induced change of optical absorption, photoluminescence, and decay time of a 0.1 mol% Yb-doped NaCl (NaCl:Yb) crystal. The crystal sample can be easily prepared from the melt using a conventional Bridgman technique. The absorption spectra showed at least four peaks at 240, 275, 340, and 380 nm owing to Yb2+, which are consistent with the excitation spectra monitored at 435 nm. The absorption rise in near-infrared owing to Yb3+ drastically decreased with increasing X-ray irradiation dose. The photoluminescence band appeared near the wavelength of 435 nm under excitation at 380 nm, which is due to the transitions from the 4f13 (2F7/2) 5d excited states to the 4f14 (1S0) ground state of Yb2+. The characteristic luminescence intensity of Yb2+ increased with increasing X-ray dose in the range from 0.1 to 100 Gy.