Dielectric conductivity of congruent lithium niobate (LiNbO3, LN) crystals was characterized by the classical method using a guard electrode on one face of the sample. The dielectric characterizations of samples are performed by current-tension measurements in the 160-300ºC temperature range. The activation energy of LN crystals is deduced by calculation from the obtained characterization experimental results. The method presented in this paper doesn't constitute a novelty itself but the overall process yielding to the determination of the activation energy of LN is originally presented, started from sample preparation to the final calculation and modeling.