With the rapid increase of bridge spans, research on controlling wind-induced vibration of long-span bridges has been a problem of great concern. In view of the fact that the vibration frequencies and damping of long-span bridges vary with wind speed, and the variation characteristics could not be accurately known even if through wind tunnel experiments, a concept of semi-active (SA) control of ind-induced vibration of long-span bridges is put forward in this paper. A new SA lever-type TMD with an adjustable frequency and the corresponding control strategy are primarily developed. A case study of the Yichang bridge, a suspension bridge with a main span of 960 m, shows that the SA lever-type TMD device is much superior to passive TMD in control efficiency and robustness.