Abstract: The nonlinear parametric vibration analysis of cable-stayed bridges is conducted using finite element method. The parametric resonances between the stay cable and the bridge deck that may occur in a certain frequency domain are identified. The semi-active control using Shape Memory Alloys(SMA)on the parametric vibrations of cable-stayed bridges is performed and the control effect for a cable-stayed bridge is numerically simulated. Results show that, after employing the SMA semi-active control, not only the parametric vibrations of the stay cable and the bridge deck can be significantly reduced, but also the parametric resonances of the cable-stayed bridge can be effectively suppressed.