Abstract: The multi-scale damage analysis method for steel box girder is presented with respect to Runyang Cable-stayed Bridge. The full-scale dynamic responses and fine-scale local damage of steel box girder are connected by the substructure method to realize structural multi-scale damage analysis. The modal curvature index, modal strain energy index, modal flexibility index and cable tension index for damage localization of steel box girder are further comparatively investigated. The analysis results show that (i) in the absence of noise, all damage indices can properly identify structural damage cases of steel box girder except the damage case of ventral plate using the modal flexibility index; (ii) for most damage cases, flexibility index is the best of the four indices in anti-noise and the cable tension index is the worst; (iii) modal strain energy index and modal flexibility index are complementary to each other in damage location identification for steel box girder.