Abstract: The flexible appendages feature a relatively low fundamental natural frequency and closely distributed low-frequency coupling modes, so for a satellite with flexible appendages and moving parts, the frequency coupling and the resonance might be an issue to affect the attitude of the satellite. To solve this problem, a method is proposed in this paper to regulate the natural frequency of the flexible appendages. Firstly, the relevant domestic and foreign studies are reviewed. Then simplified model of a spring with unidirectional stiffness on a simple beam is established, and the effect of the brace stiffness on the system modes is analyzed. A dynamical model of the active tension cable and the flexible appendages is built for simulations, to test the influence of the stiffness of cable on the system modes, and to obtain the force on and the best position of the cable. At last, the complete device is designed, with validation by ground test and flight experiment.