To improve the understanding of the damping behavior of fiber ropes, a novel method for calculating the internal damping coefficient of these ropes based on the theory of structural dynamics (TSD) is proposed. By comparing the damping values from the ‘indicator diagram’ method (IDM) utilizing experimental data of aramid, polyester and HMPE ropes, the proposed TSD method clearly shows the relation between the internal damping coefficient and dynamic stiffness of the fiber ropes. The relative error of the internal damping coefficients calculated by these two methods is small, which proves the accuracy of the TSD method. In addition, the experimental results of HMPE ropes show that the area of the hysteresis loop remains almost constant after the samples had experienced sufficient number of load cycles. The test results also indicate that the damping coefficient increases with increasing mean load, but decreases with increasing load amplitude and load periods. Hence, the present study can help developers capture the internal damping behavior of fiber ropes, leading to an efficient technology for mooring analysis, and allowing efficient implementation of the viscoelastic concept of fiber mooring ropes to engineering applications.