Abstract: In this paper the nonlinear mechanical model for parametric vibration problem of cable-stayed bridges is presented and studied with numerical method. It is pointed out that the parametric response may occur in a cable stayed bridge due to the deck vibration under certain conditions. Based upon the numerical calculation, a TMD system under the bridge deck is proposed to serve as a possible damping system. It is shown that the cable's parametric vibration of the cable stayed bridge with TMD damping system is reduced significantly.