The multibody system dynamic equations of pin and two-dimensional pointing mechanism with clearance are obtained by using “contact-separation” two-state model and the multibody system dynamic theory. Based on these equations, the dynamics characteristics are analyzed by using dynamic simulation software ADAMS. The trajectories center pin and collision force change regularities are obtained in gravity field and micro gravity field at different speeds. The simulation results show that the release of gravity has great influence on the trajectories, vibration, penetration depth, collision force and end-effector precision of clearance joint. The results have important value and great significance for clearance mechanism design.