In this paper, the damping characteristics of Nielsen-Lohse bridge is discussed based on the energy evaluation method. The damping values of Nielsen-Lohse bridge with a span length of 236m are analyzed to grasp the contribution of dissipation energy from diagonal suspender ropes. The numerical analyses are also performed by using full scale measurements of the Aki bridge to identify the loss factor of the diagonal suspender ropes. From these calculation results, some pieces of useful information for the damping characteristics are obtained to investigate the aerodynamic stability of Nielsen-Lohse bridges.