KH2O4 single crystals have been studied by employing complex impedance measurements in view of the domain freezing effect. As a result, distinct behaviors of the anisotropic domain-wall dynamics in the activation energy of domain freezing and the Vogel-Fulcher temperature before and after Proton irradiation have been identified in the anisotropic crystal structure. (c) 2009 Elsevier B.V. All rights reserved.