In order to understand the effects of coupling vibration between girder and cable on performance of cable dampers, the model comprised by cable, girder and damper is founded to study the effects. Dimensionless and complex modal analysis methods are applied to analyze the relationship between the coupling vibration mentioned above and the performance of cable damper. Results with and without the coupling vibration are compared for discussion. The results indicate that the performance of cable damper will decrease greatly when the coupling vibration happens. The higher the degree of coupling is, the worse the effect of cable damper is. The small absolute displacement of damper′s piston caused by the very small vibration phase shift of girder and cable is the main cause of the negative impact mentioned above.