Reactivity is one of the most important quantities of a nuclear reactor because it is directly related to reactor core control. In a recent paper, Altahhan et al. (2016) derived a telegraph model of the point reactor kinetics equations considering variable separation and mono-energetic neutron approximation. In this paper the inverse point kinetics equation based on the telegraph model was obtained. The power history was calculated by the partial derivatives method as proposed by Diaz et al. In order to assess reactivity accuracy considering the approximations involved in this model, simulations were performed for different exponential power and relaxation time. The results for reactivity as obtained from the proposed inverse point reactor equation show that it has significant differences in a comparison with conventional formalism, being more pronounced as the relaxation time increases.