Abstract: The static mechanical model of a cable-supporting system for Large Radio Telescope is derived on the basis of the elastic expression of a catenary. From the model, the static stiffness matrix is deduced according to the nonlinear relationship between the end force of the cable and the cabin displacement, and then we obtain the analytical expression for twist stiffness. In order to enhance the twist stiffness, a method adding a star-shaped frame on cabin is proposed and the structural parameters of the star-shaped frame are optimized. The numerical result shows that a star-shaped frame with proper parameters will enhance the twist stiffness significantly.