Abstract: To implement the automatic docking for replenishment at sea,a 6-RUS parallel mechanism is presented to realize real-time adjustment of position and orientation for bell mouth docking.First,the relative position and structure constraints of the legs of the mechanism are discussed,and the inverse kinematics model is developed.Next,the force situation of the legs of the mechanism is analyzed theoretically.And then the inverse dynamics model using Kane's equation is developed.The numerical simulation is developed to solve the evolution of drive angle and drive torque in the moving process of the mechanism.The simulation results show that the proposed kinematics model of 6-RUS parallel mechanism can predict the drive angle and torque exactly,so that the model can provide a sound theoretical basis for automatic docking in replenishment at sea.