In view of the feed drive components of 2(3PUS+S) parallel mechanism, a new idea and method for the stiffness analysis are proposed and studied.The parallel mechanism was used of a linear module as the drive component, and the overall stiffness was mainly determined by the stiffness of the ball screw. The three components of the rigidity of the ball screw pair and the stiffness of the bearing support were simplified in the calculation, taking into account the elastic deformation of the ball and the raceway at the surface contact point under the working condition of the ball screw pair, and the deformation of the joint between the ball screw and the bearing, combined with the theoretical knowledge of theoretical mechanics and Hertz contact theory, the ball screw stiffness, the axial stiffness of the ball screw and the axial stiffness of the bearing were derived separately, and finally integrated to get the stiffness of the entire system. The method is clear in concept and simple in calculation. The research results provide a basis for the stable operation of the parallel mechanism and the optimization of dynamic performance.