In this paper, a suspension gravity compensation system (SGCS) is modeled and the corresponding controller is designed. The system is a servo platform consisting of three sub-systems by which a micro-gravity environment can be established. Especially, a novel zero stiffness suspension sub-system and a creative unconstrained structure are proposed. The system model is deduced based on Lagrange equation. A PID controller is designed by using the feedback linearization approach. Simulation results show the effectiveness of the proposed method.