The invention discloses a damping vibration-reduction device for long slings in a suspension bridge. The damping vibration-reduction device comprises a supporting frame and further comprises two dampers and a connecting piece; and the two dampers are hinged to the supporting frame through hinging joints, as for configuration, after the two dampers are connected with the slings, an included angle less than 90 degrees is formed, and the connecting piece is used for fixed connecting of the two slings which are connected with the two dampers correspondingly. According to the damping vibration-reduction device, vibration in all directions of the slings is absorbed through the two dampers in the arrangement mode that the included angle is formed between the dampers, and in addition, due to the fact that the dampers are multi-modal broadband dampers, the good controlling role can be played on multiple modes of vibration.