The present invention provides large-amplitude vertical-torsional coupled free vibration testing device for bridges in natural winds, which comprises a rigid model, light-weight high-strength thin strings, linear extension springs, a rigid framework, spring protection tubes, a turntable, a rigid column, a motor, heavy blocks, and rigid thin circular rods. Based on the device, free vibration tests of a bridge deck rigid model can be carried out in natural wind with good conditions, and hence the large-scale wind tunnel device is no longer required. The scaling ratio of the rigid model is no longer limited by the wind tunnel size as in a traditional test, and the scaling ratio can be much larger. Compared with traditional wind tunnel test, the device is more suitable for large-amplitude vibration tests since it can reduce the geometrical nonlinearities of the extension springs and the blocking ratio.