The present invention belongs to the technical field of wind-induced vibration control study of bridges, and provides a dangling net cloth device for suppressing flutter of a sea-crossing bridge, i.e., a large-area dangling net cloth equipped with multiple balance weights, which is suspended below a girder by ropes and is immersed in water . When wind-induced vibration occurs on a bridge, the device is driven to move in the water, and gravity of the device as well as a huge additional mass force and an additional damping force produced by the water on the net cloth will do negative work on the girder to consume vibration energy of the bridge and effectively suppress large vibration of the bridge. The device adopts lightweight standardized components which are convenient to install, detach, transport, and store, and has the advantages of safety, reliability, economy, and practicality.