Abstract: The mechanics principle of the cable-driven parallel mechanism in the feed support system of FAST (five-hundred-meter aperture spherical radio telescope) is analyzed. Firstly, catenary model of a single cable in static equilibrium state is established considering both the dead-weight and elastic deformation of the cable. Then, the length-varying cable element is described by the absolute nodal coordinate formulation, and the dynamic model of the whole cable is obtained further. The dynamic equation of six-cable-driven parallel mechanism is obtained by using the constraint between the cable and the feed-cabin, and the constraint of the cable outlet point. Finally, the numerical calculation and simulation of the established model are carried out, speed of the cable in the operation of FAST is substituted into the model for verification. The simulation results show the influence of the dynamic characteristics of the cable on the pose of the feed-cabin, and the consistency of the simulation data of the feed cabin pose and the trend of the actual observation data, where the maximum relative error is not more than 20%.