Abstract: To enrich the measured database of the modal parameters of the long-span cable-stayed bridge， based on the data collect? ed by the structural health monitoring system of the Sutong Bridge， the modal parameters of the bridge during 2010 are obtained us? ing the established automated modal identification and tracking method. On that basis， the variability of the modal parameters of the bridge with the changing temperature and wind speed is analyzed. Results show that the frequency of the bridge is controlled by both temperature and wind speed. The frequency decreases with the increased temperature and increases with the increased wind speed. The variability of the damping ratio of the main girder of the bridge is significantly greater than that of the frequency. The damping ratio of the first-order lateral bending modes of the main girder fluctuates between 0.5% and 15% at low wind speed inter? val. It gradually decreases and stabilizes at about 2% when the wind speed is greater than 9 m/s. The damping ratio of the first four vertical bending modes of the bridge is mainly affected by the aerodynamic damping. It increases slightly with the increase of wind speed at the low wind speed intervals. The obtained results can provide a reference for assessing the in-service performance and is? suing operational management of the bridge.