Abstract: In order to investigate the damping properties of CFRP cables and establish an evaluation method for this problem, the damping properties of CFRP cables, steel cables, CFRP wires and steel wires are tested by the free vibration decaying of cables and wires. The structural damping and aerodynamic damping properties of cables are analyzed using energy dissipation principle and vibration theory respectively. It is shown that, for steel cable, the correlation between damping and strain energy ratio is significant, and the tested damping agrees with the calculated one by energy dissipation theory of strain. But for CFRP cable, a distinction exists between the tested and calculated damping. For wires with length of 1.8 m, the correlation between tested damping and strain is small. The damping caused by cable support is not negligible.