Based on the Hertz contact theory of elastic mechanics, a static stiffness model of double ball screws joint was built by analyzing the linear stiffness of double linear guide rails and the axial stiffness of double ball screw and ball bearing. The permanent magnet linear synchronous motor’s normal force affected the deformation of the feeding system. Based on the static stiffness model, deformation of the tool point was analyzed by finite element method and compared with the experimental results. The simulation results were in good agreement with measured data and indicated the accuracy of the static stiffness model. 