In order to build an accurate virtual material model for the joint of ball screw feed system,the method for obtaining parameters of virtual material model of joint based on multiobjective optimization was proposed.The analytical model of the virtual material parameters for the joint of ball screw feed system was established by using fractal theory, and the preliminary optimization interval of the virtual material parameters of the joint was obtained.Based on the multiobjective optimization method, the parameters of the virtual material model for the joint of ball screw feed system were obtained, and the two parameters acquisition methods were verified by experiments.The results show that the vibration mode of the ball screw feed system with timevarying characteristics will change with the position of the worktable.The main reason is that the length of the lead screw between the output shaft of the servo motor and the worktable will be changed with the change of the worktable position, which will affect the rigidity of the system.