Abstract: Lunar rover plays an important role in the lunar exploration. Lunar gravity is an important environmental factor concerning the locomotion performance of the rover, which has to be simulated in the ground test. In this paper, a lunar gravity simulation system (LGSS) is proposed based on the cable suspension method, and the modeling and the dynamic analysis of the control servomechanism of the cable in constant tension in the LGSS, as the key issue of the system, are specially addressed. By discretizing the cable into a series of mass-spring-damping systems, a multiple body system is obtained in place of a continuous elastic system, and then the numerical method is applied to study the dynamics of the cable system. The parameters, such as the point mass, the stiffness and the damping of the cable, are analyzed to improve the design of the lunar gravity simulator.