A 30 000 t lifting floating dock is taken as the research object in order to better grasp the characteristics of its roll motion and analyze the floating state change law. According to the characteristics of floating dock itself, the roll damping system of floating dock is designed by the robust control principle. Based on the idea of sensitivity minimization, the roll damping control system of floating dock is simulated. Through the analysis, it is found that the ability of damping control system to suppress the wave interference can meet the set interference suppression requirements.