The aim of this paper is to present the dynamic behavior of two co-axial rotating shafts connected by a reluctance magnetic coupling. The analysis is based on nonlinear differential equations of motion. The reluctance magnetic coupling is modeled by an equivalent torsional stiffness coefficient and an additional viscous damping coefficient to account for the effects of induced currents in the salient-pole during the transient. These coefficients are obtained from 3D finite element electromagnetic models. In order to evaluate the accuracy of the proposed model, several transient responses for the shaft line are considered. The simulation results are compared with those obtained from measurements.