Abstract: A new type of 2-UPR/2-RPU redundant parallel robot is proposed and used as the research object. The dynamic modeling and dynamic comparison research of it is carried out by using the spiral theory and Lagrangian method. First, the closed vector method is used to establish the kinematic inverse equation of the 2-UPR/2-RPU parallel robot in the global coordinate system; Secondly, the Lagrangian method is used to solve the velocity relationship of each component of the parallel robot and its dynamic model is established; Then, the velocities and accelerations of the joints and rods in the four branches of the parallel robot are analyzed using the screw theory, at the same time, the dynamic model of the parallel robot is established based on the principle of virtual work; Finally, based on the dynamic model of the parallel robot, the algorithm of the parallel mechanism is obtained by programming in MATLAB, and the numerical simulation results of the driving force of each branch chain of the dynamic model is established based on the screw theory and Lagrangian equation are obtained. The simulation verification and error analysis are carried out through the dynamic simulation results with ADAMS software.The results show that the dynamic model established by the screw theory has relatively high accuracy, convenient method and simple calculation, and is more suitable for the establishment of the dynamic model of the parallel mechanism with few degrees of freedom and the control of the mechanism dynamics; it greatly improves the 2-UPR/2-RPU,the response speed and control accuracy of the parallel robot meet the precision requirements of the grinding machine for grinding curved surfaces, which provides a reliable theoretical basis and an important foundation for the practical application of the mechanism.