Abstract: In this study, the effect of coupling vibration between girder and cable on the damping performance of various types of nonlinear dampers attached to a stay cable is investigated. The model composed of cable, girder and damper is established and the complex mode method is used to analyze the relationship between the girder’s parameters and the performance of cable-related nonlinear damper. The equivalent viscosity over one cycle of vibrations of the cable is estimated on the basis of the equivalent value of absorbed energy. Thus, an equivalent modal damping ratio is obtained that depends on the damper characteristics, displacement and girder’s parameters. The results show that the performance of cable-related nonlinear damper will decrease greatly when the girder’s frequencies are near the frequencies of cable.