Ag doped congruent lithium niobate crystal has been demonstrated as a promising photorefractive material for holographic recording applications. In this paper, the effects of Ag doping on the lattice structure and the optical properties were investigated by XRD, Raman spectroscopy and optical absorption characterization. The Ag ion was proposed to occupy Li-sites and results in lattice deformation. The band gap became narrower and an absorption band at near 500 nm was created with Ag doping. High temperature annealing and UV irradiation were performed to further understand the Ag doping effects. (C) 2010 Elsevier B.V. All rights reserved.