Abstract: The automobile engine tensioner is an important component of the automobile engine belt system, which generates vibration during the working process. It is a difficult task to quantitatively calculate the mechanical properties of the tensioner. In this paper, the tensioner in the automobile engine belt system is selected as the research object, and the mechanical model is established for the vibration generated by the tensioner during the working process. The dynamic moment balance equation and dynamic energy balance equation of the mechanism are established as well. The calculation model is established with the work of each torque, and the method of numerical calculation of this model is also established. Combined with a specific example, the influences of the relevant parameters on the mechanical properties of the tensioner are studied, giving rise to the influence curves. The swing angle θ of the tensioner becomes smaller with the increase of the spring stiffness G₂ when other parameters unchanged. The increase of the friction coefficient of the damping structure will make the vibration amplitude of the tensioner be smaller. With the fluctuation range of the tension increasing, the vibration range of the tensioner becomes larger. As the length L of the rotating arm increases, the amplitude of the tensioner will increase.