Abstract
In this paper we study a homothetic vector field of a Bianchi type-I model based on Lyra geometry. The cases when a displacement vector is function of t and when it is constant are considered. In both two cases we investigate the equation of state. A comparison between the obtained results, using Lyra geometry, and that have obtained previously in the context of General Relativity, based on Riemannian geometry, will be given.