Aiming at the characteristics of easy deformation and vibration of ball screw under the action of external force, the three-dimensional assembly model of ball screw is established by using SolidWorks software, and then it is simplified into ANSYS Workbench software. After setting the constraint conditions and meshing the model, the modal analysis is carried out to obtain the first six natural frequencies and vibration modes of ball screw. The results show that the first six vibration modes of ball screw are bending deformation, and the middle position's vibration amplitude of the screw is the largest in the natural frequency of the sixth order, which is the weak link of ball screw.