Experimental methods and parameters to evaluate the dynamic performances of an automatic tensioner in engine Front End Accessory Drive (FEAD) system are discussed. The dynamic performances of a tensioner include dynamic stiffness and loss angle. The influences of the pre-torque, excitation amplitude and excitation frequency on the dynamic characteristics of tensioner are measured and investigated. Considering the pre-torque, spring stiffness and damping coefficient of tensioner, and the moment of inertia for the tensioner arm, a hysteresis model used for modeling the relations between the torque and angular displacement of a tensioner is proposed. Parameters of the model are identified by the optimization process in the least-squares sense. The dynamical properties of a tensioner are calculated and compared well with experimental data, which validate the presented hysteresis model. Moreover, the equation of rotational vibration for a tensioner arm in a FEAD system is established. In the equation, dynamic stiffness and equivalent damping of a tensioner is used and is calculated based on the hysteresis model of the tensioner. Then, the rotational vibration responses of the FEAD system are calculated and compared well with experimental data, which validate the modeling method of hysteresis model and the calculation method of dynamic performances for a tensioner described in this paper.